A– LEVEL TOPIC REVIEW
unit M1
dynamics of a particle 2
If a numerical value of g is required, take g = 9.8 ms-2.
Give all non-exact answers correct to 3 significant figures unless otherwise specified.
1. a) A particle of mass 5 kg is travelling in a straight line at 10 ms-1. Find its momentum in Ns.
(2 marks)
b) A body travelling in a straight line at 36 km h-1 has 60 Ns of momentum. Find its mass.
(3 marks)
-1
c) A body of mass 4 kg moving with velocity 24 ms receives an impulse of magnitude 52 Ns
in the direction of its motion. Find its speed after the impulse is applied.
(3 marks)
2. a) A ball, of mass 20 grams, hits a wall at 15 ms-1 and rebounds along the same straight line at 9
ms-1 in the opposite direction. Find, in Ns, the change in the momentum of the ball.
(3 marks)
-1
b) A car of mass 1.4 tonnes, initially travelling at 8 ms , accelerates while travelling in a
straight line. As a result, its momentum is increased by 7000 Ns. Find its final velocity.
(3 marks)
3. Two trucks A and B, of masses 20000 kg and 15000 kg respectively, collide while moving
towards each other in a straight line. Before the collision, both trucks are travelling at 5 ms-1.
After the collision, A is moving at 1 ms-1, its direction of motion having been reversed. Find
a) the impulse exerted on A by B in the collision,
(3 marks)
b) the velocity of B after the collision, stating its direction.
(5 marks)
4. A rifle, of mass 2.4 kg, fires a bullet of mass 54 g horizontally at 360 ms-1. Find
a) the gain in momentum of the bullet when it is fired,
b) the speed at which the rifle recoils when the shot is fired.
(2 marks)
(3 marks)
5. A, B and C are three smooth spheres, whose masses and radii are equal. They are placed in a
straight groove on a horizontal table, with B between A and C. A is projected towards B with
speed 1.5 ms-1. The collision between A and B reduces A’s speed to 0.5 ms-1.
a) Find the speed of B after this collision.
(3 marks)
b) B then goes on to strike C. Immediately afterwards, B’s velocity remains the same in
magnitude but its direction is reversed. Find the speed of C after this collision.
(3 marks)
6. Two bodies A and B have masses 3 kg and 5 kg respectively. They are initially moving in the
same direction along the same straight line with velocities 5.5 ms-1 and 1.5 ms-1 respectively.
They collide and move on together as a single body, coming to rest after 5 seconds. Find the
coefficient of friction between the combined body, modelled as a particle, and the plane.
(8 marks)
7. Water is sprayed horizontally onto a vertical wall from a pipe in the form of a cylinder with a
circular cross-section of diameter 5 cm. The water strikes the wall at 12 ms-1. Calculate the
magnitude of the force exerted by the water on the wall, stating any assumptions made.
(The density of water is 1000 kg m-3).
(9 marks)
A– LEVEL TOPIC REVIEW : ANSWERS
unit M1
dynamics of a particle 2