BISHOPS
GRADE 12
PHYSICAL SCIENCE PAPER 1 – PHYSICS - MAY 2013
Examiner:
DL
Moderator: GR
Time: 3 hr
Marks: 150
This paper consists of 11 pages (including this cover sheet), an answer sheet and a data sheet.
General Instructions:
1. Answer ALL the questions.
2. Question 2: Follow the instructions below.
3. Leave one line open between subsections of questions.
4. Answer each new question at the top of a page i.e. on the back of the
previous question.
5. Calculations: Show your working. Give answers to 2 decimal places
6. Refer to the attached data sheet where necessary
Requirements:
Pocket calculator
INSTRUCTIONS FOR QUESTION 2
1.
2.
3.
4.
5.
6.
7.
Answer this question on the printed answer sheet enclosed with your question paper.
Use only a PENCIL on your answer sheet.
In the case of a wrong answer, erase the pencil marks completely.
Do not make any other marks on your answer sheet.
Four possible answers indicated by A, B, C and D, are supplied with each question. Choose
only that answer which in your opinion is the correct or best one and mark the appropriate
block on your answer sheet.
Each question has only one correct answer.
If more than one block is marked no marks will be awarded for that answer.
Example
QUESTION: The symbol for the unit for measurement of time is
A sec
B secs
C s
D S
ANSWER
A
B
C
1
D
Question One: One word answers.
Give ONE word /term for each of the following descriptions. Write the correct
word/term next to the question number (1.1 – 1.5) on the attached answer sheet.
(You may remove it from your question paper.)
1.1
1.2
1.3
1.4
The product of an object’s mass and its velocity.
A collision in which kinetic energy is conserved.
The motion of an object dropped off a high building.
The ratio of the charge stored on a pair of parallel plates to the voltage
applied across the plates.
The property of a battery which results in the operating voltages in the
circuit being lower than its emf.
1.5
(5 x 1 = 5)
Question Two: Multiple Choice.
(Answer this question on the answer sheet provided.)
2.1
In the diagram, the mechanical energy of the system is conserved. This can best be
represented mathematically as …………………
m
A)
B)
C)
D)
2.2
Ep = E k
Ep = Ek + ET
ET = E p + E k
Ek = Ep + ET
h
The force experienced by a charge q1 when placed a distance d from another charge q2
is F. When the distance between these two forces is halved, the force will increase by
a factor of ..............
A)
B)
C)
D)
1,5
2,0
3,0
4,0
2
2.3
The relationship between the magnitude of a force with which an object is
accelerated and the time for which the force acts are plotted on the following graph.
Force
Time
The area under the graph represents……….
A)
B)
C)
D)
2.4
the change in momentum of the object.
the displacement covered by the object.
the acceleration of the object.
the velocity attained by the object.
Which of the following graphs represents the relationship between velocity and time for a
perfectly elastic ball that falls from rest and bounces back to its initial height if
downwards is taken as the positive direction?
A
B
v
(m.s -1 )
0
C
D
v
(m.s -1 )
v
(m.s -1 )
v
(m.s -1 )
t (s)
0
0
t (s)
3
0
t (s)
t (s)
2.5
When a fuel tanker delivers fuel to a petrol station the action of pumping the fuel may
result in some static electricity. The driver always connects a copper wire to a grounded
metal pipe in the station near to his truck. This is to.........
A)
B)
C)
D)
2.6
allow current to pass to his pump in the truck to save some energy.
prevent a spark from jumping to earth and causing a fire.
keep his truck from rolling off the forecourt.
prevent his battery from going flat.
An athlete completes the 100m race at the Olympics in a time of 10,0s. If
his mass is 90kg then which of the velocity and kinetic energy combinations
below would be most likely just before he crosses the finish line?
Velocity/m.s-1
>10m.s-1
<10m.s-1
>10m.s-1
10m.s-1
A
B
C
D
2.7
Kinetic Energy/J
<4500
>4500
>4500
4500
Two equal masses travel towards each other on a frictionless air track at speeds of
0,6m.s-1 and 0,4m.s-1 as indicated in the diagram. They stick together on impact.
0,6m.s-1
0,4m.s-1
What is the speed of the combined masses in m.s-1 after impact?
A)
B)
C)
D)
0,1
0,2
0,4
0,5
4
2.8
Which of the following pairs of forces is not a valid example of action and reaction to
which Newton’s third law applies?
A)
B)
C)
D)
2.9
The electric field strength at a point between two charged parallel plates is 600V.m-1 at
a point 6mm from the positive plate. What is the field strength (in V.m-1) at a point
6mm from the negative plate?
A)
B)
C)
D)
2.10
The weight of a book resting on a table and the force of the table up on
the book.
The forces of repulsion experienced by two spheres carrying identical
charges and separated by a distance d.
The forces of attraction between and an electron and a proton in the
hydrogen atom.
The force of gravitational attraction exerted by the earth and the moon
on each other.
0
-600
600
1200
A Christmas tree is lit by twenty light bulbs which are connected in parallel. The light
bulbs are each marked by the manufacturer as “10W; 250V.” If all the bulbs are burning
at the same time when connected to a 250V supply voltage, what is the combined
current which they draw.
A)
B)
C)
D)
0,25A
4,00A
2,50A
0,80A
10 x 2 = /20/
5
Long Questions:
Please answer these questions on the paper provided. Show all calculations clearly on your
answer scripts.
Question Three:
3.1
A submarine approaches a frigate which stationary at anchor. The submarine, under
water, moves against a current of 3m•s-1. The torpedo in the submarine is launched
at a velocity of 18m•s-1 from the submarine. The submarine is moving at 12m•s-1
relative to the water. A lookout on the bridge of the frigate sees the submarine moving
towards the frigate.
3.1.1 What is the velocity of the submarine relative to the frigate? Show all your
working.
(3)
3.1.2 Given that the frigate is 800m away how long does the captain have before
the torpedo is likely to hit the frigate?
(3)
3.2
The “up and under” is one of the more useful kicks available to the skilled rugby player
as, executed properly, it gives the side the opportunity of competing for the ball after it
has been kicked. In a match, ‘Piston’ executes his up and under poorly and it goes
exactly vertical. The initial velocity of the rugby ball is 24m∙s-1 vertically upward. Ignore
the effects of air friction.
3.2.1 How high above the point it was kicked does the rugby ball go after
being kicked?
3.2.2 The ball is caught by the lock, ‘Kapstok’, 4,8 seconds after it has
been kicked into the air by Piston. At what height above the ground did
‘Kapstok’ catch the ball?
3.2.3. During the time that the ball is in the air, ‘Piston’, who was running at
5m∙s-1 when he kicked the ball, continues to run forward at that speed.
How far has he run before ‘Kapstok’ catches the ball?
6
(4)
(4)
(3)
3.3
A tractor is pulling 2 trailers numbered 1 and 2 along a road. They are connected by
rope to the tractor and each other. For the purpose of this problem we will ignore both
the mass of the rope and the frictional forces experienced by the trailers.
300kg
Trailer 1
300kg
T
Trailer 2
1500N
3.3.1 Draw a force diagram labelling all the forces acting on trailer 2.
3.3.2 Calculate the acceleration of the system of the trailers.
3.3.3 Calculate the tension, T in the rope.
3.4
(4)
(4)
(3)
A mechanic attends a lecture on Newtonian mechanics thinking it has something to do
with the latest in fuel injected engines. At the end of the evening he thinks he is now a
fully fledged physicist. At work the next day he proudly proclaims to his mates that,
according to Newton’s third law one cannot push start a motor car because, he says
“If you push on the car with a force F then the car pushes back on you with an equal
and opposite force F and so these two forces result in equilibrium which means that
the car will not accelerate and so you cannot push start a car”
3.4.1 Critically analyse this statement indicating where the error in the mechanics
reasoning is and how he has misunderstood Newton’s third law.
(3)
/31/
7
Question Four:
4.1
Two roller coaster tracks are of identical length and vertical height. Track A, shown
in Figure 1, is concave. Track B is a straight slope shown in Figure 2.
15m
h
h
B
A
Figure 1
Figure 2
Two roller coaster carts of equal weight (80kg each) and dimensions, start from rest at
the top of each slope of height h = 4,5m. Assume that frictional forces acting on the
track and the effects of air resistance on the roller coaster carts' motion on track A are
negligible while on track B friction is considered.
4.1.1 State the Work-Energy theorem in words.
(2)
4.1.2 What would be the work done by gravity on the cart on track A?
(3)
4.1.3 What would the velocity of the cart be at the bottom of track A?
(4)
4.1.4 Use the work energy theorem to determine the velocity of the cart at the
bottom of the track B if the frictional force experienced by the cart is 20N and
the length of the track is 15m.
(5)
4.2
A super ball (a ball that rebounds very well) of mass 50 g is thrown hard against a hard,
smooth wall, striking it with a velocity of 15 m.s-1 perpendicular to the wall. The ball
rebounds with a velocity of 14,5 m.s-1
4.2.1 Calculate the momentum of the ball before it strikes the wall.
(3)
4.2.2 Calculate the change in momentum of the ball.
(4)
4.2.3 If the contact time between the ball and the wall is 0,03s, calculate
the force exerted by the wall on the ball.
(4)
/25/
8
Question Five:
5.1
In a Millikan-type experiment, a charged oil droplet of mass 1 x 10-12g hangs
motionless between two oppositely charged parallel plates as shown. The plates
are 20mm apart and the potential difference between them is 250V.
+
+
+
+
+
+
+
 oil droplet
-
-
-
-
-
-
-
5.1.1 Draw the electric field pattern between the plates.
5.1.2 Calculate the magnitude of the electric field strength between the
two plates.
5.1.3 What is the sign of the charge on the oil droplet?
5.1.4 Calculate the magnitude of the charge on the oil droplet.
5.2
(4)
(3)
(1)
(5)
A capacitor is a device used in a variety of electrical circuits. Study the circuit diagram
below and then answer the questions that follow. The capacitor is initially uncharged.
100 V
S
Y
10 k
5.2.1 The dimensions of each plate of the capacitor is 1,5 x 103 mm by 3 x 103 mm
and the distance between the plates is 6,55 mm. There is no di-electric
between the plates. Calculate its capacitance.
(4)
5.2.2 How would the capacitance of the capacitor change if a di-electric were to be
introduced in between the plates? (Increase, decrease or stay the same) (1)
5.2.3 What will be the polarity of the plate of the capacitor marked Y?
(1)
5.2.4 Sketch each of the following graphs to show what happens in the capacitor when
the switch is closed (capacitor is charging).
a)
Potential difference across the capacitor v time.
(2)
b)
Current in the circuit v time
(2)
9
5.3
Two identical insulating spheres carrying equal but opposite charges are placed 2m
apart. The electrostatic force between them is 2,68N.
5.3.1 Calculate the charge on each sphere.
(4)
5.3.2 If the two spheres are now brought into contact with each other and then
separated to the same distance what would the force between them be?
Explain your answer.
(3)
5.3.3 Calculate field strength E at a point 10 cm from a point charge which has a
charge of 8 x 10-6C.
(4)
/34/
Question Six:
6.1
A wind farm makes use of the dynamo effect in order to produce electricity from wind.
6.1.1 Explain the dynamo effect in your own words.
(2)
6.1.2 Give 2 reasons why “farming wind” is so important.
(2)
6.1.3 How might one increase the output of a dynamo in the wind turbines?
Give two possible ways in which this can be done.
(2)
6.1.4 Where in the Western Cape would you suggest situating such a wind farm?
Support your suggestions with scientific as well as economic reasons
(3)
6.2
In the following diagram the brushes supply current to the coil via the split ring
commutator.
6.2.1 State Fleming’s left hand motor rule in words.
(2)
6.2.2 In which direction does the coil rotate if one is looking down the axis of the
commutator? (Clockwise or anti-clockwise)
(1)
6.2.3 What is the function of the split ring commutator?
10
(2)
6.3
Consider the following circuit diagram. The battery has an emf of 6V and an
internal resistance of 0,8Ω. The resistance of the ammeter is negligible.
2Ω
4Ω
12Ω
2Ω
S
A
Emf = 6V
r = 0,8Ω
6.3.1 Calculate the effective resistance of the parallel combination.
6.3.2 When the switch is open, calculate the reading on the ammeter.
6.3.3 When the switch is closed, what will happen to the brightness of the
bulb? Explain your answer.
6.3.4 What happens to the ammeter reading? Explain your answer.
6.4
(3)
(4)
(3)
(3)
Most of the electricity to our homes and industry is supplied in the form of
alternating current. (A.C)
6.4.1 Name one of the benefits of generating current for use as AC.
6.4.2 What does the abbreviation ‘rms’ stand for?
6.4.3 If a kitchen appliance has an Imax rating of 15A, what current does it
actually operate at?
6.4.4 If it also operates at 220Vrms, what would its power rating be?
Grand Total
11
(1)
(1)
(3)
(3)
/35/
{150}