TEST ON MOMENTUM
TOTAL :: 25
f/m/16/2/2
Q.1 Fig. 2.1 shows a hammer being used to drive a nail into a piece of
wood.
hammer head
nail
wood
Fig. 2.1
SI
R
The mass of the hammer head is 0.15 kg.
The speed of the hammer head when it hits the nail is 8.0 m / s.
The time for which the hammer head is in contact with the nail is 0.0015 s.
The hammer head stops after hitting the nail.
S
(a) Calculate the change in momentum of the hammer head.
AN
change in momentum = ...........................................................[2]
(b) State the impulse given to the nail.
H
impulse = ...........................................................[1]
(c) Calculate the average force between the hammer and the nail.
average force = ...........................................................[2]
[Total: 5]
1
f/m/17/42/2
Q.2
(a) Explain why momentum is a vector quantity.
...............................................................................................................................................[1]
(b) The crumple zone at the front of a car is designed to collapse during a collision.
crumple
zone
SI
R
concrete wall
Fig. 2.1
In a laboratory test, a car of mass 1200 kg is driven into a concrete wall, as shown in Fig. 2.1.
Calculate
(ii)
the change of momentum of the car,
H
(i)
AN
S
A video recording of the test shows that the car is brought to rest in 0.36 s when it collides
with the wall. The speed of the car before the collision is 7.5 m / s.
change of momentum = ...........................................................[2]
the average force acting on the car.
average force = ...........................................................[2]
2
© UCLES 2017
0625/42/F/M/17
5
(c) A different car has a mass of 1500 kg. It collides with the same wall and all of the energy
transferred during the collision is absorbed by the crumple zone.
(i)
The energy absorbed by the crumple zone is 4.3 × 105 J. Show that the speed of the car
before the collision is 24 m / s.
[2]
Suggest what would happen to the car if it is travelling faster than 24 m / s when it hits
the wall.
R
(ii)
...........................................................................................................................................
[Total: 8]
H
AN
S
SI
.......................................................................................................................................[1]
3
© UCLES 2017
0625/42/F/M/17
[Turn over
f/m/20/42/2
Q.3
Fig. 2.1 shows an athlete crossing the finishing line in a race. As she crosses the finishing line,
her speed is 10.0 m / s. She slows down to a speed of 4.0 m / s.
SI
R
Fig. 2.1
S
(a) The mass of the athlete is 71 kg. Calculate the impulse applied to her as she slows down.
(b) (i)
AN
impulse = ........................................................ [3]
Define impulse in terms of force and time.
...........................................................................................................................................
(ii)
H
..................................................................................................................................... [1]
The athlete takes 1.2 s to slow down from a speed of 10.0 m / s to a speed of 4.0 m / s.
Calculate the average resultant force applied to the athlete as she slows down.
force = ........................................................ [2]
(c) Calculate the force required to give a mass of 71 kg an acceleration of 6.4 m / s2.
4
force = ........................................................ [2]
[Total: 8]
© UCLES 2020
0625/42/F/M/20
[Turn over
m/j//17/1/2
Q.4
A footballer kicks a ball vertically upwards. Initially, the ball is stationary.
(a) His boot is in contact with the ball for 0.050 s. The average resultant force on the ball during
this time is 180 N. The ball leaves his foot at 20 m / s.
Calculate
the impulse of the force acting on the ball,
H
AN
S
SI
R
(i)
impulse = ...........................................................[2]
(ii)
the mass of the ball,
5
mass = ...........................................................[2]
(iii)
the height to which the ball rises. Ignore air resistance.
height = ...........................................................[3]
(b) While the boot is in contact with the ball, the ball is no longer spherical.
State the word used to describe the energy stored in the ball.
...............................................................................................................................................[1]
[Total: 8]
© UCLES 2017
0625/41/M/J/17