- Force
- |
- Law's Of motion
- |
- First Law of Motion
- |
- Momentum
- |
- Second Law of Motion
- |
- Third Law of Motion
- |
- Law Of conservation of Momentum

(b) A bullet of mass 0.02 kg is fired from a gun weighing 7.5 kg if the initial velocity of bullet is 200 m/s. Calculate the speed with which the gun recoils.

a) A person is hit harder, when the person falls on a hard floor than when he falls on sand or cotton.

b) A gunman gets jerk in backward direction while firing a gun.

c) A bullet fired on a glass window makes a fine hole while a stone smashes when hits it.

(i) What is meant by momentum of a body? How can it be measured? Write its SI units.

(ii) Explain how does Newton’s first law give the qualitative definition of force?

a) Which will have greater inertia?

b) Which will have greater momentum?

c) Which will stop first if equal negative acceleration is applied on both?

d) Which will travel greater distance?

e) Which will impart greater impulse if collides with a wall?

ii) How much momentum will an object of mass 10 kg transfer to the floor if it falls from a height of 5 m? (g = 10 m/s

(iii) Explain how a karate player can break a pile of tiles with a single blow of his hand.

A runner presses the ground with his feet before he starts his run.

To take the boat away from the bank of a river, the boat man pushes the bank with an oar.

A karate player can break a slab of ice with a single blow of his hand.

(b) A boy of mass 60 kg running at 3 m/s jumps on to a trolley of mass 140 kg moving with a velocity of 1.5 m/s in the same direction.

Find their common velocity.

Using this law explain why a gun recoils.

(b) Two cars each of mass 1000 kg are moving in a straight line but in opposite directions. The velocity of each car is 5 m/s before the collision during which they stick together. What will be the velocity of the combined cars after collision?

(b) A car and a truck have same momentum. Whose velocity is more and why?

(c) A bullet of mass 20 g moving with a speed of 500 m/s strikes a wooden block of mass 1 kg and gets embedded in it. Find the speed with which block moves along with the bullet.

(b) A hammer of mass 500 g moving with 50 m/s strikes a nail. The nail stops the hammer in a small time interval of 0.01/s. what is the change in momentum suffered by the hammer? Also calculate the force of the hammer on the nail. What will be the force of the nail on the hammer? Give reason for your answer.

(ii) An object of mass 50 kg is accelerated uniformly from a velocity of 4 m/s to 8 m/s in 8 s. calculate the initial and final momentum of the object. Also find the magnitude of the force exerted on the object.

INTERESTING NUMERICALS

1. A bullet of 10 g strikes a sand bag at a speed of 10

(i) the resistive force exerted by the sand on the bullet.

(ii) the time taken by the bullet to come to rest.

2. A force of 5 N produces an acceleration of 8 m/s

3. A hammer of mass 500 g, moving at 50 m/s, strikes a nail. The nail stops the hammer in a very short time of 0.01 s. what is the force of the nail on the hammer?

Class 9 Maths Class 9 Science