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Scheme of work – Cambridge International AS Level Physical Science (8780)
PHYSICS – SECTION II
Unit 2: Newtonian mechanics
Recommended prior knowledge
Students should be able to describe the action of a force on a body. They should able to describe the motion of a body and recognise acceleration and constant
speed. They should be able to use the relationship average speed = distance moved / time taken. A study of aspects of Unit PH1 is necessary for the
understanding of the quantities and units involved.
Context
Motion, force, energy and power are important aspects of physics e.g. waves and oscillations. As such, work studied in this Unit will be applied to all other units.
Outline
The motion of objects is studied using graphical and mathematical techniques. The concept of momentum is introduced and conservation laws related to collisions
are studied. Energy conservation is extended to cover work done in different situations and also efficiency. Power is introduced as rate of doing work or dissipation
of energy.
Syllabus ref
Learning objectives
Suggested teaching activities
Learning resources
Sections 3(a) to 3(e) is revision work from IGCSE and although it needs
revisiting, time spent covering this should be appropriately limited.
There is a limited supply of past papers
for the 8780 examination, therefore all
past paper questions are taken from
Physics 9702 AS papers. These reflect
the type of question that candidates are
likely to meet in the 8780 examinations.
Candidates should be able to:
P3(a)
describe the action of a force on a
body
Discussion: forces acting on bodies cause a change in motion.
Examples of pushes on trolleys, why do trolleys slow down? Why do
bodies fall to the ground?
P3(b)
describe the motion of a body and
recognise acceleration and
constant speed
Use of ticker timer to or stroboscopic photos to demonstrate acceleration
and constant speed.
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Cambridge International AS Level Physical Science (8780)
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Syllabus ref
Learning objectives
Suggested teaching activities
Learning resources
P3(c)
recall and use the relationship
average speed = distance / time
Calculation of average speed of a runner over a measured distance
Analysis of ticker tape from above.
If available: motion sensor, data logger
and display to plot displacement of a
pendulum bob etc.
P3(d)
define displacement, speed,
velocity and acceleration
Discussion: distinction between distance moved
and displacement
distinction between speed and
velocity
meaning of acceleration /
deceleration / retardation
Formal definitions.
P3(e)
use graphical methods to
represent displacement, speed,
velocity and acceleration
Revision of graph plotting.
Displacement/time graphs:
Velocity / time and speed / time graphs:
recognition of constant velocity / speed
constant acceleration / deceleration
Past paper
May/June 2010, 9702 Paper 21,
question 2
See the Mathematical Requirements as
given in the syllabus.
P3(f)
recall that the weight of a body is
equal to the product of its mass
and the acceleration of free fall
Discussion: what is weight?
CD of astronauts on the Moon
P4(a)
describe and use the concept of
weight as the effect of a
gravitational field on a mass
Above discussion leads to; weight = mass × g
g can be measured in either m s–2 or N kg–1
P5(b)
describe the forces on mass and
charge in uniform gravitational
and electrical fields, as
appropriate
Discussion: force on mass is
– in direction of the field (acceleration)
– independent of speed of mass
– equal to mg
Past papers
May/June 2009, 9702 Paper 22,
question 2(a)(b)
Oct/Nov 2007, 9702 Paper 1,
question 10
P5(d)
show an understanding that the
weight of a body may be taken as
acting at a single point known as
its centre of gravity
Discussion: what is centre of gravity?
refer briefly to centre of mass
Experiment: determination of C.G. of a lamina
P4(b)
show an understanding that mass
is the property of a body which
Discussion: what is mass?
v2 2Y07
Cambridge AS Level Physical Science (8780)
lamina, pin and cork, plumbline, stand,
boss, clamp
2
Syllabus ref
Learning objectives
Suggested teaching activities
Learning resources
resists change in motion
P4(e)
recall and solve problems using
the relationship F = ma,
appreciating that acceleration and
force are always in the same
direction
Discussion: what causes an acceleration?
Experiment: relation between force and acceleration.
Equations F ∝ a, F = ma, m and a are base/derived units, leading to
definition of the unit of force (Newton).
Past papers
May/June 2008, 9702 Paper 2,
question 3(a)
Oct/Nov 2008, 9702 Paper 2,
question 2
Oct/Nov 2007, 9702 Paper 2,
question 2
Oct/Nov 2007, 9702 Paper 1,
question 12
P3(g)
describe qualitatively the motion
of bodies falling in a uniform
gravitational field with air
resistance
Effect of air resistance:
– air resistance increases with speed.
Discussion of motion of body falling through air:
– increasing speed gives rise to increasing drag and reducing
acceleration thus leading to terminal speed.
Dropping steel spheres and ping pong
balls in air.
‘Guinea and feather’ experiment.
www.nuffieldfoundation.org/practicalphysics/guinea-and-feather
Experiment – dropping steel spheres and table tennis balls in air.
‘Guinea and feather’ experiment.
Apparatus: steel ball bearings of different sizes (or masses of different
sizes) table tennis balls
Past paper
Oct/Nov 2009, 9702 Paper 21,
question 2
table tennis balls, steel balls of various
diameters, stopwatch, metre rule
demonstrate an understanding
that a force applied to a body at
right angles to the velocity of the
body causes a change in
direction of the body
‘Monkey and the Hunter’ experiment – used to illustrate the effect of
gravity on a projectile motion.
P3(i)
demonstrate an understanding of
circular motion including
centripetal acceleration
Discussion / demonstration of circular motion e.g. mass on a spring,
water in a bucket.
P4(c)
define linear momentum as the
product of mass and velocity
Discussion: idea of ‘violence’ of a collision depends on mass and
velocity
P3(h)
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‘Monkey and the Hunter’ experiment
www.ap.smu.ca/demos/
Demonstration of deflection of electrons in deflection tube
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Syllabus ref
Learning objectives
Suggested teaching activities
Learning resources
P4(d)
define force as the rate of change
of momentum
Develop definition of momentum.
Definition of force, discuss this is more general than F = ma as a
definition of force.
– direction of force / change in momentum
Worked example of rocket motor.
ticker timer, tape, trolleys, elastic
bands, metre ruler
and/or
linear air track, timers, metre rule
and/or
trolleys and runway, motion sensor,
data logger and means of display
objects with different masses –
estimating masses
newton balances, estimating forces
Exercise on base units of N kg–1 and m
s–2.
P4(g)
apply the principle of
conservation of momentum to
solve simple problems including
elastic and inelastic interactions
between two bodies in one
dimension. (knowledge of the
concept of coefficient of
restitution is not required)
Idea of a ‘collision’ and a closed system.
Statement of law of conservation of momentum.
Experiment: ‘Verification’ of the law
Worked examples (illustrated if possible) including:
– colliding spheres (newton’s cradle)
– impact of a ball with a solid surface
– magnetic/electrostatic interaction
Past papers
May/June 2010, 9702 Paper 22
question 3
May/June 2009, 9702 Paper 21
question 2
Oct/Nov 2009, 9702 Paper 21,
question 3
site 1
P4(f)
understand the difference
between elastic and inelastic
collisions
P5(a)
show a qualitative understanding
of frictional forces including air
resistance
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Discussion: elastic and inelastic collisions to show that, while momentum
of a system is always conserved in interactions between bodies, some
change in kinetic energy usually takes place.
Conservation (or otherwise) of total energy, linear momentum and
kinetic energy.
Examples of elastic and inelastic collisions.
two trolleys and masses, runway, two
timers, ticker tape
OR
linear air track, two timers and light
gates
OR
use of trolleys / linear air track with
motion sensors, data loggers and
means of display
Newton’s cradle air table (if available)
linear air track (if available)
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Syllabus ref
Learning objectives
Suggested teaching activities
P5(e)
show an understanding that a
couple is a pair of forces which
tends to produce rotation only
Discussion: force(s) producing rotation.
Single force – turning effect and moment of
a force.
P5(f)
define and apply the moment of a
force and the torque of a couple
Two forces – a couple and torque (turning effect) of a couple.
P5(g)
show an understanding that,
when there is no resultant force
and no resultant torque, a system
is in equilibrium
P5(h)
apply the principle of moments
Learning resources
Discussion: what is meant by equilibrium?
– no resultant force in any direction
– no resultant moment about any point
Principle of moments defined (as one condition for equilibrium).
Experiment: verification of principle.
Worked examples.
suspended metre rule, newton meters,
thread, protractor
site 2
use a vector triangle to represent
forces in equilibrium
Past papers
May/June 2009, 9702 Paper 21,
question 3
Oct/Nov 2007, 9702 Paper 1,
question 14
May/June 2011, 9702 Paper 21,
question 3
Oct/Nov 2011, 9702 Paper 21,
question 2
P5(c)
P6(b)
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show an understanding of the
concept of work in terms of the
product of a force and the
displacement in the direction of
the force
Discussion: equilibrium of a body under the action of three forces
– lines of action must pass through one point
– revision of vector triangles and use for
forces in equilibrium
metre rule, pin and cork, stand, boss,
clamp, thread, various weights, pulley,
protractor
Revision and discussion: what is work?
– definition of work done
– units
– Nm = J
Past papers
Oct/Nov 2009, 9702 Paper 11,
question 13
Oct/Nov 2008, 9702 Paper 2,
question 3
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Syllabus ref
Learning objectives
Suggested teaching activities
P6(f)
show an understanding of and
use the work done when a force
moves its point of application in a
uniform field is equal to the
potential energy change
Define energy as the capacity to do work.
P6(g)
derive, from the defining equation
W = F ∆s, the formula Ep = mg ∆h
for potential energy changes near
the Earth’s surface
Ep = mg ∆h derived as an example of use
of W = F ∆s
P6(d)
understand the concept of
gravitational potential energy,
electrical potential energy and
elastic potential energy
Give examples and relate to 6(b) and (f).
P6(e)
recall and apply the formula EK =
½ mv2
Discussion of energy due to movement.
Examples, emphasise need to remember to square the velocity.
P6(h)
recall and use the formula Ep =
mgh for potential energy changes
near the Earth’s surface
Potential energy changes discussed.
P6(i)
show an understanding of the
concept of internal energy
Internal energy as sum of random kinetic energy and potential energy of
atoms.
Difference between random and ordered kinetic energy (avoid the use of
terms thermal and heat energy).
P6(a)
give examples of energy in
different forms, its conversion and
conservation, and apply the
principle of energy conservation
to simple examples
Revision and summary of work and energy.
examples of energy transfers, e.g. discussion: Ek – Ep exchanges
e.g. simple pendulum, falling object
leading to principle of conservation of energy.
Worked examples
P6(j)
show an appreciation for the
implications of energy losses in
Discussion of efficiency, define the efficiency of a system as the ratio of
useful work done by the system to the total energy input.
v2 2Y07
Cambridge AS Level Physical Science (8780)
Learning resources
Past papers
May/June 2011, 9702 Paper 22,
question 3
Oct/Nov 2011, 9702 Paper 21,
question 4
6
Syllabus ref
Learning objectives
Suggested teaching activities
Learning resources
practical devices and use the
concept of efficiency to solve
problems
Energy ‘losses’ related to energy conservation.
Role of friction forces.
Efficiency defined.
Experiment: efficiency of an electric motor.
voltmeter, ammeter or joulemeter. Low
voltage motor, thread, weights,
stopclock, metre rule.
P6(c)
define power as work done per
unit time
Discussion: what is power? Revision from IGCSE
Experiment: power and efficiency of a boy running upstairs carrying a
bucket of water (remember the useful work done is lifting the water only!)
P6(k)
derive power as the product of
force and velocity
Derivation from power = work done / time.
P6(l)
solve problems using the
relationships power = work done
per unit time and power = force x
velocity
Worksheet / homework
v2 2Y07
Cambridge AS Level Physical Science (8780)
Stairs, bathroom scales, metre rule,
stopclock
Past paper
May/June 2011, 9702 Paper 22,
question 3
7