VCE PHYSICS UNIT 3
ÊÊÊÀˆ>˜Ê-…>`܈VŽÊUÊ̈Ìʅ>À}>Û>
Study Design
2009
© Science Press 2009
First published 2009
Science Press
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Science Press. ABN 98 000 073 861
Contents
Introduction
v
Verbs to Watch
vi
Dot Points
Motion in One and Two Dimensions
vii
Electronics and Photonics
ix
Einstein’s Special Theory of Relativity
xi
Materials and Their Use in Structures
xiii
Further Electronics
xv
Questions
Motion in One and Two Dimensions
1
Electronics and Photonics
89
Einstein’s Special Theory of Relativity
129
Materials and Their Use in Structures
171
Further Electronics
215
Answers
Motion in One and Two Dimensions
263
Electronics and Photonics
279
Einstein’s Special Theory of Relativity
287
Materials and Their Use in Structures
295
Further Electronics
303
Appendix
Data Sheet
312
Science Press
Dot Point VCE Physics Unit 3
iii
Contents
Notes
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Science Press
Contents
iv
Dot Point VCE Physics Unit 3
Introduction
What the book includes
In this book you will find typical examination questions and answers for each dot point in the VCE Physics
Study Design for the following topics in the Year 12 course:
s
-OTIONIN/NEAND4WO$IMENSIONS
s
%LECTRONICAND0HOTONICS
s
%INSTEINS3PECIAL4HEORYOF2ELATIVITY
s
-ATERIALSAND4HEIR5SEIN3TRUCTURES
s
&URTHER%LECTRONICS
Format of the book
The book has been formatted in the following way:
1.1 etc
Area of Study knowledge statement.
Note that the numbering of these statements is the authors’ choice and has been used to make referencing
questions and answers clearer. The individual knowledge statements are not numbered in the study design,
they are simply bulleted – hence our use of ‘dot points’ when we refer to them.
1.1.1 First typical question which could be asked in an examination for dot point 1.1
1.1.2 Second typical question which could be asked in an examinaton for dot point 1.1.
Note also that some questions using the same stimulus diagrams may not relate to the same dot point as the
first question using that diagram.
How to use the book
Completing all questions will provide you with an overview of all the work you need to know from the study
design. You may have done work in addition to this with your teacher as extension work. Obviously this is not
covered, but you may need to know this additional work for your school exams, but not for the VCE.
When working through the questions, write the answers you have to look up in a different colour to those you
know without having to research the work. This will provide you with a quick reference to work you should
spend more time revising later, and allow you to spend your study time more productively.
Science Press
Dot Point VCE Physics Unit 3
v
Introduction
Verbs to Watch
account/account for
State reasons for, report on, give an account of,
narrate a series of events or transactions.
distinguish
Recognise or note/indicate as being distinct or
different from, note difference between things.
analyse
Identify components and the relationships among
them, draw out and relate implications.
evaluate
Make a judgement based on criteria.
examine
Inquire into.
apply
Use, utilise, employ in a particular situation.
explain
Relate cause and effect, make the relationship
between things evident, provide why and/or how.
appreciate
Make a judgement about the value of something.
extract
Choose relevant and/or appropriate details.
assess
Make a judgement of value, quality, outcomes,
results or size.
extrapolate
Infer from what is known.
calculate
Determine from given facts, figures or information.
identify
Recognise and name.
clarify
Make clear or plain.
interpret
Draw meaning from.
classify
Arrange into classes, groups or categories.
investigate
Plan, inquire into and draw conclusions about.
compare
Show how things are similar and different.
justify
Support an argument or conclusion.
construct
Make, build, put together items or arguments.
outline
Sketch in general terms; indicate the main features.
contrast
Show how things are different or opposite.
predict
Suggest what may happen based on available data.
critically (analyse/evaluate)
Add a degree or level of accuracy, depth, knowledge
and understanding, logic, questioning, reflection and
quality to an analysis or evaluation.
propose
Put forward (a point of view, idea, argument,
suggestion etc) for consideration or action.
deduce
Draw conclusions.
recall
Present remembered ideas, facts or experiences.
define
State the meaning of and identify essential qualities.
recommend
Provide reasons in favour.
demonstrate
Show by example.
recount
Retell a series of events.
describe
Provide characteristics and features.
summarise
Express concisely the relevant details.
discuss
Identify issues and provide points for and against.
synthesise
Put together various elements to make a whole.
Science Press
Verbs to Watch
vi
Dot Point VCE Physics Unit 3
Motion in One and Two Dimensions
Dot Point
Page
Dot Point
Page
3
1.8
Analyse transformations of energy
between kinetic energy, strain potential
energy, gravitational potential energy,
and energy dissipated to the environment.
63
Analyse the uniform circular motion
of an object moving in a horizontal
plane.
19
1.9
Apply gravitational field and
gravitational force concepts.
73
79
Apply Newton’s second law to circular
motion in a vertical plane, considering
forces at the highest and lowest points
only.
27
1.10 Apply the concepts of weight,
apparent weight, weightlessness
and apparent weightlessness.
1.11 Model satellite motion as uniform
circular motion.
83
1.4
Investigate and analyse the motion of
projectiles near the Earth’s surface
including a qualitative description of
the effects of air resistance.
33
1.12 Identify and apply safe and responsible
practices when working with objects
and equipment in investigations of motion.
87
1.5
Apply laws of conservation of
momentum and energy in isolated
systems.
41
1.6
Analyse impulse in an isolated system,
for collisions between objects moving
in a straight line.
49
1.7
Apply the concept of work done
by a constant force.
57
1.1
Apply Newton’s three laws of
motion in situations where two
or more coplanar forces act along
a straight line and in two dimensions.
1.2
1.3
Answers to Motion in
One and Two Dimensions
263
Science Press
Dot Point VCE Physics Unit 3
vii
Motion in One and Two Dimensions
Space
Notes
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Science Press
Motion in One and Two Dimensions
viii
Dot Point VCE Physics Unit 3
Electronics and Photonics
Dot Point
Page
2.1
Apply the concepts of current,
resistance, potential difference
(voltage drop) and power to the operation
of electronic circuits comprising diodes,
resistors, thermistors and photonic
transducers including LDRs,
photodiodes and LEDs.
91
2.2
Calculate the effective resistance of
circuits comprising parallel and series
resistance and unloaded voltage dividers.
99
2.3
2.4
Describe energy transfers and
transformations in opto-electronic
devices.
107
Describe the transfer of information in
analog form using light intensity
modulation and demodulation.
111
Dot Point
Page
2.5
Design, investigate and analyse
circuits for particular purposes using
technical specifications related to
potential difference, current, resistance,
power, temperature and illumination for
electronic components such as diodes,
resistors, thermistors, LDRs,
photodiodes and LEDs.
115
2.6
Analyse voltage characteristics of
amplifiers including linear voltage gain
and clipping.
119
2.7
Identify and apply safe and
responsible practices when
conducting investigations involving
electrical, electronic and photonic
equipment.
127
Answers to Electronics and Photonics
279
Science Press
Dot Point VCE Physics Unit 3
ix
Electronics
Motors and
andGenerators
Photonics
Notes
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Science Press
Electronics and Photonics
x
Dot Point VCE Physics Unit 3
From Ideas
Einstein’s
Special
to Implementation
Theory of Relativity
Dot Point
3.1
3.2
3.3
Describe the prediction from
Maxwell’s equations that the speed
of light depends only on the electrical
and magnetic properties of the medium
through which it is passing, and not on
the speed of the source or the speed of
the medium.
Page
Dot Point
131
Compare the prediction from Maxwell’s 133
equations of an absolute speed of light
with the classical principle of relativity,
i.e. no absolute zero velocity; all velocity
measurements are relative to the frame
of reference.
Describe Einstein’s two postulates for
his special theory of relativity and
compare them to classical theory:
s T HELAWSOFPHYSICSARETHESAME
in all inertial frames of reference
s T HESPEEDOFLIGHTHASACONSTANT
value for all observers regardless
of their motion or the motion of the
source.
3.6
Explain the concepts of proper time (to)
and proper length (Lo) as quantities that
are measured in the frame of reference
in which the objects are at rest.
3.7
Explain the unfamiliar nature
151
of motion at speeds approaching c by
mathematical modelling time dilation and
length contraction using the equations:
Interpret the results of the
Michelson-Morley experiment in
terms of Einstein’s second postulate.
139
3.5
Apply simple thought experiments
to show that:
147
s T HETIMEINTERVALBETWEENTWO
events differs depending on the
motion of an observer relative to
the events (non-simultaneity)
s LENGTHCONTRACTIONOFANOBJECT
occurs in the direction of its motion
when observed from a different
frame of reference.
149
t = toȖ and L = Lo/Ȗ where Ȗ= (1 – v2/c2)–½
3.8
Apply Einstein’s prediction by showing
that the total mass-energy of an object
is given by Etot = Ek + Erest = mc2
where m = moȖ and so kinetic energy,
Ek = (Ȗ – 1)mc2
163
3.9
Explain that mass can be converted
into energy and vice versa, E = ǻmc2
165
135
3.4
Page
3.10 Explain the impossibility of motion
faster than light in terms of relativistic
mass m = mo at speeds approaching c.
169
Answers to Einstein’s Special Theory
of Relativity
287
Science Press
Dot Point VCE Physics Unit 3
xi
Einstein’s
From
Special
IdeasTheory
to Implementation
of Relativity
Notes
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Science Press
Einstein’s Special Theory of Relativity
xii
Dot Point VCE Physics Unit 3
From Ideas
Materials
and
to Their
Implementation
Use in Structures
Dot Point
4.1
4.2
4.3
4.4
Page
Identify different types of external
forces such as compression, tension
and shear, that can act on a body,
including gravitational forces.
173
Evaluate the suitability of different
materials for use in structures,
including beams, columns and arches,
by comparing tensile and compressive
strength and stiffness or flexibility
under load.
177
Dot Point
Analyse the behaviour of materials
181
under load in terms of extension and
compression, including Young’s
modulus, Y = σ .
ε
Calculate the stress and strain resulting 187
from the application of compressive and
tensile forces and loads to materials in
structures, σ = F , ε = Δl
A
Describe brittle and ductile failure and
apply data to predict brittle or ductile
failure under load.
4.6
Calculate the potential energy stored
191
in a material under load (strain energy)
using area under the stress versus strain
graph.
4.7
Evaluate the toughness of a material
tested to the point of failure.
193
4.8
Describe elastic or plastic behaviour
of materials under load and the
resulting energy transformed to heat
195
4.9
Evaluate the suitability of a composite
material for its use in a structure by
considering its properties and the
properties of the component materials
(maximum of three components).
197
4.10 Calculate torque,
.
201
4.11 Analyse translational and rotational
205
forces (torques) in simple structures,
including uniform columns, struts, ties,
beams, cables, but not including trusses,
modelled as two-dimensional structures
in static equilibrium.
4.12 Identify safe and responsible practices
213
when working with structures, materials
and associated measuring equipment in
investigations of materials.
l
4.5
Page
189
Answers to Materials and Their
Use in Structures
295
Science Press
Dot Point VCE Physics Unit 3
xiii
Materials andFrom
Their Quanta
Use in Structures
to Quarks
Notes
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Materials and Their Use in Structures
xiv
Dot Point VCE Physics Unit 3
From Ideas
Further
Electronics
to Implementation
Dot Point
5.1
Page
Design and investigate an AC to
DC voltage regulated power supply
system, given a range of AC input
voltages (specified as RMS, peak
and peak-to-peak), smoothing
conditions and resistive loads.
217
Describe the role of a transformer,
including the analysis of voltage
ratio, N1/N2 = V1/V2, but not
including induction.
219
5.3
Describe effects on the DC power
supply system of changes to the
components used.
221
5.4
Interpret information from the display
of an oscilloscope in terms of voltage
as a function of time.
227
5.5
Analyse circuits, including fault
diagnosis, following selection and
use of appropriate measuring devices,
including analog meters, multimeters,
and oscilloscope.
229
5.2
5.6
5.7
Dot Point
Evaluate the operation of a circuit in
231
terms of its design brief by selecting
measurements of potential difference
(voltage drop) and current (using analog
meters, multimeters and oscilloscope)
in the DC power supply circuit.
Explain the function of diodes in
half-wave and full-wave bridge
rectification.
Page
5.8
Explain the effect of capacitors in
terms of:
239
s POTENTIALDIFFERENCEVOLTAGEDROP
and current when charging and
discharging
s TIMECONSTANTFORCHARGINGAND
discharging, IJ = RC
s SMOOTHINGFOR$#POWERSUPPLIES
5.9
Apply the current-voltage
characteristics of voltage regulators,
including Zener diodes and integrated
circuits, to circuit design.
245
5.10 Describe, qualitatively, the effect on
the magnitude of the ripple voltage of
changing the effective load, the
capacitance and input supply voltage
(magnitude and period).
251
5.11 Describe the use of heat sinks in
electronic circuits.
255
5.12 Calculate power dissipation in circuit
elements, P = VI, P = I2R, P = V 2/R.
257
5.13 Identify and apply safe and responsible
responsible practices when undertaking
investigations involving electrical
and electronic equipment.
259
Answers to Further Electronics
303
235
Science Press
Dot Point VCE Physics Unit 3
xv
Further
Astrophysics
Electronics
Notes
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Science Press
Further Electronics
xvi
Dot Point VCE Physics Unit 3
DOT POINT
œÌˆœ˜Êˆ˜Ê"˜iÊ>˜`Ê/ܜʈ“i˜Ãˆœ˜Ã
Science Press
Dot Point VCE Physics Unit 3
1
Motion in One and Two Dimensions
Notes
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Science Press
Motion in One and Two Dimensions
2
Dot Point VCE Physics Unit 3
1.1 Apply Newton’s three laws of motion in situations where two or more coplanar
forces act along a straight line and in two dimensions.
1.1.1
Recall Newton’s first law of motion.
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1.1.2
Explain the relationship between Newton’s first law of motion and the concept of inertia.
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1.1.3
Explain, in terms of the principles of physics involved, why it is potentially dangerous to leave loose
objects on the back shelf of a car.
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1.1.4
Explain, in terms of the principles of physics involved why it is dangerous to drive a car without wearing
a seatbelt.
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1.1.5
Identify two real-life situations where Newton’s first law of motion is apparent, and explain how this
affects the person involved.
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Science Press
Dot Point VCE Physics Unit 3
3
Motion in One and Two Dimensions
1.1.6
Identify two real-life situations where Newton’s first law of motion is not apparent, and explain why it is
not apparent.
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1.1.7
Explain the role of the inertia of passengers in each of the following situations. For each situation,
outline what forces do act on the passenger (ignore weight force and reaction to weight force).
(a)
The school bus turning a corner.
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(b)
A plane accelerating down the runway.
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(c)
A lift in a high-rise building starting to move upwards.
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(d)
A lift in a high rise building starting to move downwards.
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Motion in One and Two Dimensions
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Dot Point VCE Physics Unit 3
1.1.8
Assess the relative effectiveness of lap, lap-sash and harness seatbelts in reducing the effects of inertia
in collisions.
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1.1.9
Assess reasons for the introduction of lower speed limits for vehicles in built-up areas.
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1.1.10 Outline how airbags work to reduce the effects of inertia.
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1.1.11 Use the principles of physics involved to explain how crumple zones reduce the effects of inertia in
collisions.
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1.1.12 The inertia of a spacecraft in deep space keeps it travelling towards its destination. The inertia of a
moving car does not – it slows and stops. Explain the reasons for the difference.
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Dot Point VCE Physics Unit 3
5
Motion in One and Two Dimensions
1.1.13 Recall Newton’s second law of motion.
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1.1.14 Recall the mathematical equation which governs Newton’s second law of motion.
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1.1.15 Calculate the force acting on a 5.0 kg mass which accelerates for 3.0 s. During this time its velocity
changes from 2.5 m s–1 east to 17.5 m s–1 west.
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1.1.16 A 12 N force acts on a body and accelerates it from rest to 4.5 m s–1 south. This takes 15 s. Calculate
the mass of the body.
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1.1.17 An 80 g object is initially at rest. A 0.16 N force to the north acts on it for 5 s. Calculate:
(a)
The acceleration produced by the force.
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(b)
The final velocity of the object.
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(c)
Its displacement after 5 s.
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Motion in One and Two Dimensions
6
Dot Point VCE Physics Unit 3
1.1.18 Consider the two blocks shown in the diagram. They are resting on a surface which provides a frictional
force of 0.25 N kg–1.
Y
X
18 N
(a)
2.5 kg
5.5 kg
Calculate the acceleration of the system.
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(b)
Calculate the net force on each block.
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(c)
Calculate the force block X puts on block Y.
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(d)
Calculate the force block Y puts on block X.
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1.1.19 Consider the two blocks shown in the diagram. They are resting on a smooth surface.
Y
X
36 N
(a)
3.0 kg
6.0 kg
Calculate the acceleration of the system.
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Dot Point VCE Physics Unit 3
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Motion in One and Two Dimensions
(b)
Calculate the net force on each block.
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(c)
Calculate the force tension in the string.
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1.1.20 Consider the object shown in the diagram. Several forces act on this object which is at rest on a
smooth, horizontal surface.
(a)
Calculate the net force on the object.
15 N
26 N
4 kg
6N
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(b)
Calculate the acceleration of the object.
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(c)
Calculate its velocity after 5.0 s
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(d)
Calculate its displacement after 5 s.
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Motion in One and Two Dimensions
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Dot Point VCE Physics Unit 3
1.1.21 Consider the two blocks shown in the diagram. They are connected by a light string over a frictionless
pulley.
X 2 kg
Y
4 kg
(a)
Label all the forces acting in this pulley system, then calculate:
(b)
The acceleration of the system.
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(c)
The net force on each block.
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(d)
The tension in the string connecting the blocks.
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Dot Point VCE Physics Unit 3
9
Motion in One and Two Dimensions
1.1.22 Consider the two blocks shown in the diagram. They are connected by a light string over a frictionless
pulley. Block X is resting on a smooth surface.
X
2 kg
Y
5 kg
(a)
Label all the forces acting in this pulley system.
(b)
Calculate the acceleration of the system.
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(c)
Calculate the net force on each block.
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(d)
Calculate the tension in the string connecting the blocks.
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1.1.23 A 3 kg mass is resting on a newton balance in an elevator. Complete the table to show the reading on
the balance under the conditions of movement of the elevator given.
Movement of elevator
Reading on newton balance
(a) Stationary
(b) Moving up at 2.0 m s–1
(c) Moving down at 2.0 m s–1
(d) Moving up at 2.0 m s–2
(e) Moving down at 2.0 m s–2
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Motion in One and Two Dimensions
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Dot Point VCE Physics Unit 3
1.1.24 Two masses are connected by a string and are hanging from the ceiling of an elevator as shown.
Complete the table to show the tensions in each string under the conditions of movement of the
elevator given.
Movement of elevator
Tension in string 1 (N)
Tension in string 2 (N)
(a) Stationary
(b) Moving up at 3.0 m s–1
(c) Moving down at 3.0 m s–1
(d) Moving up at 3.0 m s–2
(e) Moving down at 3.0 m s–2
1.1.25 A ball is hanging by a string from the ceiling of a bus. Describe the motion of the bus when the string is:
(a)
Hanging straight down.
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(b)
Hanging down towards the rear of the bus.
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(c)
Hanging down towards the front of the bus.
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Dot Point VCE Physics Unit 3
11
Motion in One and Two Dimensions
1.1.26 A 3.0 kg ball is hanging by a string from the ceiling of a bus as shown in the diagram.
(a)
Label the forces acting on the ball.
10º
3 kg ball
(b)
Using an appropriate vector diagram, calculate the tension in the string when the ball is in the position
shown.
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(c)
Calculate the acceleration of the bus.
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(d)
At what angle would the ball and string hang if the bus was breaking at 2.5 m s–2?
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Motion in One and Two Dimensions
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Dot Point VCE Physics Unit 3
1.1.27 Analysing an experiment 1.
Trolley
Pulley
Mass
In this experiment, a trolley of mass 1.5 kg was placed on the bench accelerated by a force attached to
it by a string, which passed over a pulley. The mass of the trolley was kept constant and different forces
used to accelerate it from rest across the benchtop. The time it took the trolley to travel 1.0 m across
the benchtop was measured. The results are shown in the table.
Run
Accelerating
force (N)
Time to travel Initial speed of
1.0 m (s)
trolley (m s–1)
1
F
0.89
2
2F
0.63
3
3F
0.52
4
4F
0.45
5
5F
0.40
Average speed
of trolley (m s–1)
Final speed of
trolley (m s–1)
Acceleration of
trolley (m s–2)
(a)
Complete the table by calculating values for all missing data.
(b)
Draw a graph to show the relationship between the force and acceleration produced. (Place force on
the y-axis.)
(c)
Use your graph to write a conclusion for the experiment.
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Dot Point VCE Physics Unit 3
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Motion in One and Two Dimensions
1.1.28 Analysing an experiment 2.
The students did another experiment using the same apparatus. This time they kept the accelerating
force constant, and changed the mass of the trolley. They measured how long it took the trolley to
move 1.0 m across the benchtop.
Run
Trolley
mass
(kg)
Time to
travel
1.0 m (s)
1
1.0
1.83
2
2.0
2.58
3
3.0
3.16
4
4.0
3.65
5
5.0
4.08
Initial
speed of
trolley
(m s–1)
Average
speed of
trolley
(m s1)
Final speed Acceleration of
trolley
of trolley
(m s–2)
(ms–1)
(a)
Complete the table of results by calculating values for all missing quantities.
(b)
Graph mass vs. (acceleration)–1.
(c)
Use your graph to write a conclusion for the experiment.
(Acceleration)–1
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Motion in One and Two Dimensions
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Dot Point VCE Physics Unit 3
Combining your conclusions for experiments 1 and 2
(d)
Use the conclusions you have written to write a mathematical equation, which shows the relationship
between the mass of an object, the force acting on it and the acceleration the force produces.
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(e)
Use the results of the experiments to find the value of the accelerating forces in the two experiments
above.
Experiment 1
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Experiment 2
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1.1.29 Maria is riding her skateboard, total mass 60 kg, down a slight incline at a constant speed of 12 m s–1.
The air is providing a resistance of 40 N and the wheels of the skates provide another 6 N of frictional
force.
(a)
What is the net force acting on Maria? Justify your answer.
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(b)
If the incline is at 10° what is the component of the weight force of Maria and her skateboard down the
incline?
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(c)
What force does the ground exert on the wheels of the skateboard in opposition to its motion?
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Dot Point VCE Physics Unit 3
15
Motion in One and Two Dimensions
1.1.30 A cyclist of mass 65 kg pedals a 35 kg bike up a 15° incline at a constant speed.
(a)
Draw a diagram and label all the forces acting in this situation.
(b)
What is the net force on the cyclist as he pedals up the incline?
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(c)
If the frictional forces against motion are 40 N, what force does the cyclist exert on the bike to ride it up
the incline?
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(d)
When he reaches the top, the rider turns around and coasts down the incline. His acceleration is
1.5 m s–2. What frictional forces oppose his motion?
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Opposing force (N)
1.1.31 A 1500 kg boat accelerates at a constant rate across the surface of a lake. As its speed increases,
the opposing forces applied to it by the water and air resistance change as shown in the graph. After
travelling 500 m it travels at constant speed.
12 000
10 000
8000
6000
4000
2000
0
0
(a)
100
200
300
Distance (m)
400
500
What total force do the engines apply to the boat after it has travelled 500 m?
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(b)
What is the net force acting on the boat after it has travelled 500 m?
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Motion in One and Two Dimensions
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Dot Point VCE Physics Unit 3
(c)
What is the force exerted by the engines as the boat reaches the 200 m mark?
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(d)
Calculate the acceleration of the boat at the instant is reaches the 300 m mark.
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1.1.32 A police officer measured the skid marks of a 1200 kg car which crashed into a barrier across the road
at 75 m long. She estimates that the frictional forces between the car and the road while it skidded
into the barrier averaged 15 000 N. If the speed limit in the area was 90 kph, and assuming the driver
applied the brakes where the skid marks start, by how much was the driver breaking the speed limit
when he first applied the brakes?
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1.1.33 State Newton’s third law of motion.
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1.1.34 Describe an example of Newton’s third law of motion.
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1.1.35 Two students are riding in a dodgem car (X) when the car behind (Y) crashes into their car. Describe the
forces on the students during this collision and indicate which of Newton’s laws of motion apply.
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Dot Point VCE Physics Unit 3
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Motion in One and Two Dimensions
Notes
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Motion in One and Two Dimensions
18
Dot Point VCE Physics Unit 3
1.2 Analyse the uniform circular motion of an object moving in a horizontal plane.
1.2.1
Two 60 kg boys on 20 kg bikes are riding at 15 m s–1 directly towards a wall which is 30 m from them.
X continues towards the wall, but slams on his brakes applying a 400 N force. Y does not put on his
brakes, but turns his bike with the same force in a circular path in the hope of not hitting the wall.
Analyse this information to determine whether or not the boys hit the wall.
(a)
For X
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(b)
For Y
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1.2.2
A toy racing car of mass 150 g is racing around a circular track of diameter 80 cm. It takes 8.4 s to do
one lap of the track. Calculate:
(a)
The speed of the car.
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(b)
The acceleration of the car.
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(c)
The centripetal force acting on the car.
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Dot Point VCE Physics Unit 3
19
Motion in One and Two Dimensions
1.2.3
A 1500 kg racing car goes around a circular track of radius 200 m at a constant speed of 270 kph.
(a)
Calculate the speed of the car in m s–1.
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(b)
Calculate the acceleration of the car.
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(c)
What force holds the car to the road as it speeds around this corner.
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(d)
Calculate the value of this force.
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(e)
State the direction this force acts.
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(f)
Predict the value of this force if the speed of the car was to halve.
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1.2.4
A toy train of mass 600 g moves around a circular track of diameter 3.0 m. The maximum frictional
force experienced by the train is 0.16 N. What is the maximum speed of the train so that it stays on the
tracks?
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Motion in One and Two Dimensions
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Dot Point VCE Physics Unit 3
1.2.5
A particular horse on a merry-go-round is 3.5 m from the centre. A 20 kg child sits on the horse as it
goes around, completing 16 revolutions in the 4-minute ride time.
(a)
What acceleration does the child experience?
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(b)
Calculate the average acceleration experienced by the child during each complete revolution.
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(c)
Calculate the horizontal speed of the child while the merry-go-round is working.
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1.2.6
The tracks at velodromes are banked to allow
cyclists to travel at very fast speeds. A particular
track is banked at 20o and has a radius of curvature
of 105 m. The diagram represents a cyclist and her
bike, total mass 75 kg, travelling at constant speed
on this track.
(a)
Draw and label any forces acting on the cyclist.
(b)
What is the component of the weight force of the
cyclist and her bike down the incline on the banked
track?
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(c)
If the track surface itself provides 15 N against slippage down the bank, what is the maximum speed
this cyclist can travel at safely?
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1.2.7
A cycling track in a park is totally flat and provides 125 N of sideways friction on each of the wheels of a
15 kg bike ridden by a 20 kg child at each corner. The radius of the curve at each of the four corners is
15 m.
Calculate the maximum safe speed the child can be going as he turns the corners.
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Dot Point VCE Physics Unit 3
21
Motion in One and Two Dimensions
1.2.8
A racing car, mass 750 kg, moving with constant speed, experiences a horizontal force of 15 000 N as it
turns an unbanked corner of radius 35 m.
(a)
What is the net force acting on the car?
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(b)
Calculate the speed of the car around the corner.
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(c)
What provides this force?
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(d)
What will be the average force on each tyre?
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1.2.9
The diagram represents a front view of the wheels of a train which is travelling towards you (out of the
page). The train is about to turn towards its left (right as you look at it).
Wheel X
Wheel Y
Train about to
turn this way
Rail X
Rail Y
(a)
On the diagram label the force(s) that cause the train to turn in the direction shown.
(b)
Referring to the principles of physics involved, justify your answer.
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Motion in One and Two Dimensions
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Dot Point VCE Physics Unit 3
1.2.10 The diagram represents a car travelling at constant
speed around a circular track. On this diagram draw
a labelled vector to indicate each of the following:
(a)
The instantaneous velocity of the car.
(b)
The acceleration of the car.
(c)
The net force acting on the car.
1.2.11 An object is travelling in uniform circular motion in a
circle of radius 0.25 m. The diagram represents a
stroboscopic photograph taken of the object over
a 0.5 s interval.
(a)
What is the speed of the object?
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(b)
What is its acceleration?
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(c)
A student now adjusts the stroboscope so that it flashes twice as fast. Complete the diagram (above)
to show what would be observed on the photograph for the next half revolution of the object.
(d)
What would be the acceleration of the object now?
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Dot Point VCE Physics Unit 3
23
Motion in One and Two Dimensions
1.2.12 A toy train of mass 250 g is travelling on a circular track of radius 50 cm, on a frictionless, horizontal
table.
(a)
What is the magnitude and direction of the force of the table on the mass?
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(b)
If the car comes off the tracks when the centripetal force is just greater than 3 × 10–2 N, what is its
maximum possible speed around the track?
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(c)
If a carriage of mass 200 g was coupled to the engine, what would be its maximum frequency of
rotation?
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1.2.13 A pilot in an aircraft will black out if his plane turns in a circle with too small a radius. The average
acceleration air force pilots can withstand is about 4 g or 39.2 m s–2. What is the tightest horizontal
circle a pilot in an aircraft flying at 950 kph can make?
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Motion in One and Two Dimensions
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Dot Point VCE Physics Unit 3
1.2.14 Two balls, X and Y are attached to the ends of light strings as shown in the diagram. They are swung in
a horizontal circle, each completing that circle in the same time despite that fact that the radius of the
circle for X is 0.3 m and that for Y is 0.2 m.
Point of suspension
X
Y
0.2 m
0.3 m
(a)
Determine the value of the ratio of the angular speed of X to that of Y.
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(b)
Determine the value of the ratio of the linear speed of X to that of Y.
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(c)
Determine the value of the ratio of the centripetal accelerations of X and Y.
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(d)
If X has a mass twice that of Y, determine the value of the ratio of the centripetal forces acting on X and Y.
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Science Press
Dot Point VCE Physics Unit 3
25
Motion in One and Two Dimensions