Numericals assignment- class IX

Q What is the momentum of a man of mass 75kg when he walks with a uniform velocity of 2m/s?

Q What is change in momentum of a car weighing 1500 kg when its speed increases from 36km/h to 72km/h uniformly?

Q A man throws a ball weighing 500g vertically upwards witha speed of 10m/s.

1) what will be its initial momentum?

2) What would be its momentum at the highest point of his flight?

Q A truck starts from rest and rools down a hill with constant acceleration. It travels a distance of 400m in 20s. Find the force acting on it if its mass is 7 metric tonnes. ( 1 metric ton= 1000kg)

Q A car of mass 2400kg moving with a velocity of 20m/s is stopped in 10s on applying brakes. Calculate the retardation and the retarding force.

Q For how long should a force of 100N act on a body of 20kg so that it acquires a velocity of 100m/s?

Q A body of mass 2kg is at rest. What should be the magnitude of force which will make the body move with a speed of 30m/s at the end of 1s?

Q An unloaded truck weighing 2000kg has a maximum acceleration of 0.5 m/s*s. What is the maximum acceleration when it is carrying a load of 2000kg?

Q The car A of mass 1500kg, travelling at 25m/scollides with another car B of mass 1000kg travelling at 15m/s in the same direction. After collision the velocity of car A becomes 20m/s. Calculate the velocity of car B after collision.

Q A bullet of mass 10g moving with a velocity of 400m/s gets embedded in a freely suspended wooden block of mass 900g. What is the velocity acquired by the block?

Q A 10g bullet travelling at 200m/s strikes and remains embedded in a 2kg target which is originally at rest but free to move. At what speed does the target move off?

Q A gun of mass 3kg fires a bullet of mass 30g. The bullet takes 0.003s to move through the barrel of the gun and acquires a velocity of 100m/s. calculate:

a) the velocity with which the gun recoils.

b) the force exerted on gunman due to recoil of the gun.

Q A ball X of mass 1kg trvelling at 2m/s has a head on collision with an identical ballY at rest. X stops and Y moves off. Calculate the velocity of Y after the collision.

Q A boy of mass 50kg running at 5m/s jumps onto a 20kg trolley travelling in the same directionat 1.5m/s. What is their common velocity?

Q A girl of mass 50kg jumps out of a rowing boat of mass 300kg on to the bank, with ahorizontal velocity of 3m/s. With what velocity does the boat begin to move backwards?

Q The velocity of a body of mass 10kg increases from 4m/s to 8m/s when a force acts on it for 2s.

a) What is the momentum before the force acts?

b) What is the momentum after the force acts?

c) What is the gain in momentum per second?

d) What is the value of the force?

Q Calculate the value of acceleration due to gravity on the surface of the moon?

Q The earth's gravitational force causes an acceleration of 5m/s*s in a 1kg mass somewhere in space. How much will the acceleration of a 3kg mass be at the same place?

Q To estimate the height of a bridge over a river, a stone is dropped freely in river from bridge. The stone takes 2s to touch the water surface. Calculate the height of bridge from the water level.

Q A cricket ball is dropped from a height of 20m

a) Calculate the speed of the ball when it hits the ground.

b) Calculate the time it takes to fall through this height.

Q A body has a weight of 10kg on the surface of the earth. What will be its weight when taken to the centre of the earth?

Q A stone resting on the ground has a gravitational force of 20N acting on it. What is the weight of the stone