Download DP Physics Unit 2 part 2 Practice Test 1. A rocket is fired vertically. At

DP Physics Unit 2 part 2 Practice Test
1.
A rocket is fired vertically. At its highest point, it explodes. Which one of the following
describes what happens to its total momentum and total kinetic energy as a result of the explosion?
Total momentum
Total kinetic energy
A.
unchanged
increased
B.
unchanged
unchanged
C.
increased
increased
D.
increased
unchanged
(1)
2.
Which of the following quantities are conserved in an inelastic collision between two bodies?
Total linear momentum of the bodies
Total kinetic energy of the bodies
A.
yes
yes
B.
yes
no
C.
no
yes
D.
no
no
(1)
3.
The momentum of a system is conserved if
A.
no external forces act on the system.
B.
no friction forces act within the system.
C.
no kinetic energy is lost or gained by the system.
D.
the forces acting on the system are in equilibrium.
(1)
4.
A ball of mass 2.0 kg falls vertically and hits the ground with speed 7.0 ms–1 as shown below.
7.0 ms –1
3.0 ms –1
before
after
The ball leaves the ground with a vertical speed 3.0 ms–1.
The magnitude of the change in momentum of the ball is
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DP Physics Unit 2 part 2 Practice Test
A.
zero.
B.
8.0 Ns.
C.
10 Ns.
D.
20 Ns.
5.
A ball is held at rest at point X and is then released. It drops on to a flat horizontal surface and
rebounds to a maximum height at point Y.
point X
point Y
before
after
Which one of the following graphs best shows the variation with time t of the momentum p of
the ball as it moves between point X and point Y?
A.
B.
p
0
p
0
t
0
C.
0
t
0 0
t
D.
p
p
0
0
t
(1)
6.
A small ball P moves with speed v towards another identical ball Q along a line joining the
centres of the two balls. Ball Q is at rest. Kinetic energy is conserved in the collision.
v
P
Q at rest
Which one of the following situations is a possible outcome of the collision between the ball
v
A. v
P
C.
3v
D.
4
4
Q
v
v=0
P
Q
v
P
B.
P
Q
v
v
2
2
Q
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DP Physics Unit 2 part 2 Practice Test
(1)
7.
A weight is suspended from a spring. The variation with weight of the length of the spring is
shown below.
length / cm
16
14
12
10
0
2
4
6
8
weight / N
What is the value of the spring constant (force constant) of the spring?
A.
0.4 N cm–1
B. 0.5 N cm–1
C. 2.0 N cm–1
D. 2.5 N cm–1
(1)
8.
The engine of a rocket ejects gas at high speed, as shown below.
rocket
high speed
gas
direction of
motion of rocket
The rocket accelerates forwards because
A.
the momentum of the gas is equal but opposite in direction to the momentum of the
rocket.
B.
the gas pushes on the air at the back of the rocket.
C.
the change in momentum of the gas gives rise to a force on the rocket.
D.
the ejected gas creates a region of high pressure behind the rocket.
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DP Physics Unit 2 part 2 Practice Test
9.
The weight of a mass is measured on Earth using a spring balance and a lever balance, as shown below.
spring balance
lever balance
What change, if any, would occur in the measurements if they were repeated on the Moon’s surface?
Spring balance
Lever balance
A.
same
same
B.
same
decrease
C.
decrease
same
D.
decrease
decrease
(1)
10. A bird of weight W lands at the midpoint of a horizontal wire stretched between two poles. The
magnitude of the force exerted by each pole on the wire is F.
F
F
W
The bird will be in equilibrium if
A.
2F > W.
B.
2F = W.
C.
2F < W.
D.
F = W.
(1)
11.
For an object to be in translational equilibrium
A.
it must be at rest.
B.
it must be moving with a constant acceleration.
C.
no external force must be acting on it.
zero.
D.
the net force acting on it must be
(1)
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DP Physics Unit 2 part 2 Practice Test
12. A constant force is applied to a ball of mass m. The velocity of the ball changes from v1 to v2.
The impulse received by the ball is
A.
m(v2 + v1).
B. m(v2 – v1).
C.
m(v22 + v12).
D.
m(v22 – v12).
(1)
13.
This question is about vectors.
A student sets up the apparatus shown below to investigate forces.
spring
balance B
spring
balance B
10 N weight
The weight of 10.0 N is suspended from spring balance A by means of a light string. Spring
balance B is also attached to the string. The spring balance B is pulled horizontally as shown.
(a)
Using the grid on the diagram, draw a scale diagram to determine the readings on each of
the spring balances.
Reading on spring balance A: ...................................................................................
Reading on spring balance B: ...................................................................................
(4)
(b)
Suggest why it is not possible for the whole length of the string joining spring balances A
and B to be horizontal with the weight still suspended.
...................................................................................................................................
...................................................................................................................................
(1)
(Total 5 marks)
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DP Physics Unit 2 part 2 Practice Test
14.
This question is about the collision between two railway trucks (carts).
(a)
Define linear momentum.
.....................................................................................................................................
.....................................................................................................................................
(1)
In the diagram below, railway truck A is moving along a horizontal track. It collides with a
stationary truck B and on collision, the two join together. Immediately before the collision,
truck A is moving with speed 5.0 ms–1. Immediately after collision, the speed of the trucks is v.
5.0 ms –1
B
A
Immediately before collision
v
A
B
Immediately after collision
The mass of truck A is 800 kg and the mass of truck B is 1200 kg.
(b)
(i)
Calculate the speed v immediately after the collision.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
(ii)
Calculate the total kinetic energy lost during the collision.
...........................................................................................................................
...........................................................................................................................
(2)
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DP Physics Unit 2 part 2 Practice Test
(c)
Suggest what has happened to the lost kinetic energy.
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 8 marks)
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DP Physics Unit 2 part 2 Practice Test
15.
This question is about conservation of momentum and conservation of energy.
(a)
State Newton’s third law.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(1)
(b)
State the law of conservation of momentum.
.....................................................................................................................................
.....................................................................................................................................
(2)
The diagram below shows two identical balls A and B on a horizontal surface. Ball B is at rest
and ball A is moving with speed V along a line joining the centres of the balls. The mass of each
ball is M.
v
Before collision
B
A
During the collision of the balls, the magnitude of the force that ball A exerts on ball B is FAB
and the magnitude of the force that ball B exerts on ball A is FBA.
(c)
On the diagram below, add labelled arrows to represent the magnitude and direction of
the forces FAB and FBA.
During the collision
B
A
(3)
The balls are in contact for a time Δt. After the collision, the speed of ball A is +vA and the
speed of ball B is +vB in the directions shown.
vA
After the collision
vB
A
B
As a result of the collision, there is a change in momentum of ball A and of ball B.
(d)
Use Newton’s second law of motion to deduce an expression relating the forces acting
during the collision to the change in momentum of
(i)
ball B.
...........................................................................................................................
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DP Physics Unit 2 part 2 Practice Test
........................................................................................................................... (2)
(ii)
ball A.
...........................................................................................................................
...........................................................................................................................
(2)
(e)
Apply Newton’s third law and your answers to (d), to deduce that the change in
momentum of the system (ball A and ball B) as a result of this collision, is zero.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
(f)
Deduce, that if kinetic energy is conserved in the collision, then after the collision, ball A
will come to rest and ball B will move with speed V.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 17 marks)
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DP Physics Unit 2 part 2 Practice Test
16.
This question is about driving a metal bar into the ground.
Large metal bars can be driven into the ground using a heavy falling object.
object
mass = 2.0×103 kg
bar
mass = 400 kg
In the situation shown, the object has a mass 2.0 × 103 kg and the metal bar has a mass of
400 kg.
The object strikes the bar at a speed of 6.0 m s–1. It comes to rest on the bar without bouncing.
As a result of the collision, the bar is driven into the ground to a depth of 0.75 m.
(a)
Determine the speed of the bar immediately after the object strikes it.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(4)
(b)
Determine the average frictional force exerted by the ground on the bar.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 7 marks)
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DP Physics Unit 2 part 2 Practice Test
17.
Momentum
(a)
State the law of conservation of momentum.
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
(2)
(b)
An ice hockey puck collides with the wall of an ice rink. The puck is sliding along a line
that makes an angle of 45 to the wall.
wall
45
45
ice rink
direction of puck
before collision
direction of puck
after collision
The collision between the wall and the puck is perfectly elastic.
(i)
State what is meant by an elastic collision.
.........................................................................................................................
.........................................................................................................................
(1)
(ii)
Discuss how the law of conservation of momentum applies to this situation.
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
(2)
(c)
The diagram below is a scale diagram that shows the vector representing the momentum
of the puck before collision.
Scale: 1.0 cm = 0.10 N s
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DP Physics Unit 2 part 2 Practice Test
By adding appropriate vectors to the diagram, deduce that the magnitude of the change in
momentum of the puck as a result of the collision is 0.71 N s.
(4)
(d)
The sketch-graph below shows the variation with time t of the force F exerted by the wall
on the puck.
F
0
0
t
The total contact time is 12 ms. Estimate, explaining your reasoning, the maximum force
exerted by the wall on the puck.
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
(3)
(Total 12 marks)
18.
This question is about momentum and energy.
(a)
Define impulse of a force and state the relation between impulse and momentum.
definition:
.....................................................................................................................................
.....................................................................................................................................
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DP Physics Unit 2 part 2 Practice Test
relation:
.....................................................................................................................................
.....................................................................................................................................
(2)
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DP Physics Unit 2 part 2 Practice Test
(b)
By applying Newton’s laws of motion to the collision of two particles, deduce that
momentum is conserved in the collision.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(5)
(c)
In an experiment to measure the speed of a bullet, the bullet is fired into a piece of
plasticine suspended from a rigid support by a light thread.
24cm
bullet
speed V
plasticine
The speed of the bullet on impact with the plasticine is V. As a result of the impact, the
bullet embeds itself in the plasticine and the plasticine is displaced vertically through a
height of 24 cm. The mass of the bullet is 5.2×10–3 kg and the mass of the plasticine is
0.38 kg.
(i)
Ignoring the mass of the bullet, calculate the speed of the plasticine immediately
after the impact.
...........................................................................................................................
...........................................................................................................................
(2)
(ii)
Deduce that the speed V with which the bullet strikes the plasticine is about
160 m s–1.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
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DP Physics Unit 2 part 2 Practice Test
(2)
(Total 11 marks)
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