TUTORIAL 3
FORCE AND MOMENTUM
1. A 900-kg car travelling at 25-ms-1 brakes hard and comes to rest in 5-s. What are the average
braking forces?
2. A child is to boganning. If the total frictional forces on the sledge is 100-N and the mass of the
child and sledge is 45-kg. Calculate the initial acceleration down a 30° slope.
3. What velocity would a ball of mass 500-g need to equal the linear momentum of 750-kg car
travelling at 20-ms-1?
4. Calculate the initial and final momentum of a 1000 g ball thrown vertically up with a speed of
10 m/s.
5. The speed of a car weighing 1000 kg increases from 36 km/h to 108 km/h. Calculate the
change in momentum.
6. A bullet of mass 0.04 kg moving with a velocity of 360 km/h is brought to rest by a target in
0.02 second. Calculate the impulsive force.
7. Determine the magnitude of the linear momentum of a 200 g hockey puck travelling at a
speed of 108 km/h.
8. A driver accelerates the car at the rate of 2 m/s2 and after some time the car starts
accelerating at the rate of 4 m/s2. Calculate the ratio of forces.
9. A baseball player hurls a 0.14 kg baseball at a speed of 46.3 m/s. What was the magnitude of
the ball’s momentum as it left his hand?
10 kg
µ=0.2
300
θ= 30°
10. A 10kg block is placed on an inclined plane with an angle of 30° with the horizontal. The
coefficient of kinetic friction between the block and the inclined plane is 0.2.
a) Draw a free body diagram to show all the forces acting on the block.
b) Determine the friction force, F acting on the block.
c) Calculate the acceleration of the block going down the inclined plane.
v
45°
v
racket
45°
tennis ball
11. A tennis ball of mass 0.2 kg and moving with 30 ms-2 strikes a tennis racket at an angle of
45°. The ball rebounds from the racket with the same speed at an angle of 45° with the racket
as shown in the diagram above. If the time taken for the ball to change direction is 0.5 s, find
a.
b.
c.
The change in momentum of the tennis ball.
The impulse experienced by the racket.
The magnitude of the impulse force on the racket
C
T1
5 kg
T1
2 kg
A
a
T2
T2
3 kg
B
12. 3 blocks A, B, and C are arranged as shown in the diagram. Find their common
acceleration, tension of the string T1 and T2 when they are released from rest.Where we
remembered in the final step to include the direction of the force in words.
A
B
13. A 4.0 kg block A on rough 30⁰ inclined plane is connected to a freely hanging 1.0 kg block B
by mass- less cable passing over the frictionless pulley as shown in figure above. When the
objects are released from the rest, object A slides down the inclined plane with friction force of
6.0 N. Calculate
I.
II.
the acceleration of the objects
the tension in the cable
F
A
B
14. Object A and B of masses 3.5kg and 2.0kg respectively are connected with a light string
across a smooth pulley as shown in figure above. At t=0, A is pulled by 30N force, F. The
coefficient of kinetic friction between block A and the table is 0.20. Calculate
I.
II.
the acceleration
the time taken by B to move upwards by 1.0m
15. The driver of a car of mass 1000kg traveling at 20.0 ms-1 on a level road suddenly applied
his brake. The car skidded 4.0m before it comes to a stop. Find the frictional force when the
brake is applied.
16. Three object of mass m1, m2 and m3 are connected by two strings over two small light
pulleys as shown in the figure. If m1 = 200g , m2 = 300g , m3 = 500g , Ө= 30° and the
coefficient of friction on boh surfaces are 0.35. find
a) The acceleration of the system
b) The tension in each string
m2
m1
m3
17. What average net force is required to bring a 1500 kg car to rest from a speed of 100 km/h
within a distance of 55 m?
18. A 10000 kg rail cord car, A travelling at a speed of 24.0 m/s strikes an identical car, B at
rest. If the cars locked together as a result of collision, what is their common speed immediately
after collision?
19. A box of mass 10 kg is placed on a smooth incline that makes an angle 300 with the
horizontal. Determine the normal force on the box and its acceleration.
20. A rocket its fires its engine, which exerts an average force of 1000 N for 4 s in a fixed
direction. What is the magnitude of the rocket’s momentum change?
21. Two balls A and B of masses 4kg and 2kg respectively are suspended by a string through a
pulley . If the system is released, find the acceleration of the system.