 # Extra questions on Force ,Momentum and Laws of Motion

Given below are the force and laws of motion class 9 extra questions and important questions
(a) Objective Type Questions
(b) Very Short questions
(c) Short questions
(e)Law of Conservation of Momentum Long answer type questions
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## Objective type

Question 1.
A passenger in a moving train tosses a coin which falls behind him. It means that motion of the train is
(a) accelerated
(b) uniform
(c) retarded
(d) along circular tracks

Question 2.
A truck of mass M is moved under a force F. If the truck is then loaded with an object equal to the mass of the truck and the driving force is halved,then how does the acceleration change?.
(a) 1/2
(b) 2
(c)1/4
(d) 1/8

## Very Short Questions

Question 1.
Explain why same of the leaves may get detached from a tree if we vigorously shake its branch?

Question 2.
An object of mass 100 kg is accelerated uniformly from a velocity of 5 m/s to 8 m/s in 6 s. Calculates the initial and final momentum of the object. Also find the magnitude of force exerted on the object.

Question 3.
Out of the four physical quantities associated with the motion of an object viz force, velocity, acceleration and momentum which one remains constant for all bodies large or small, undergoing a free fall?

Question 4.
A runner presses the ground with his feet before he starts his run. Identify action and reaction in this situation.

Question 5.
An athlete always runs some distance before taking a jump. Why?

Question 6.
How are action – reaction forces related in magnitude and direction?

Question 7.
State the relation between the momentum of a body and the force acting on it.

Question 8.
(i) A heavy and a light object have same momentum. Which of these is travelling faster?
(ii) State the law of conservation of momentum. Give examples.

Question 9.
What is the effect force, when it is applied in the following cases?
a.Balloon is pressed from opposite sides.
b.A ball is hit with a bat.
c.Spring is compressed.

Question 10.
If you are trying to push a heavy box on a horizontal surface, list various forces acting on the box. State the condition under which this box will start sliding on the surface. How will the magnitude of applied force required to move the box change if:
(a)Weight of the box is increased?
(b)The surface on which the box is placed is made more rough? Question 11.
A pile of carom coins is hit with a fast sliding strike. What happens to the carom coins and why?
Question 12.
A stone released from the top of a tower of height 19.6 m. calculate its final velocity just before touching the ground.

Question 13.
A gun of mass 3 kg fires a bullet of mass 30 g. the bullet takes 0.003 s to move through the barrel of the gun and acquires a velocity of 100 m/s. calculate:
(a)The velocity with which the gun recoils.
(b)The force exerted on gunman due to recoil of the gun.

Question 14.
(i)Define SI unit of force. (ii)A force of 2 N acting on a body changes its velocity uniformly from 2 m/s to 5 m/s in 10 s. calculate the mass of the body.

Question 15.
Why is it advised to tie the luggage with a rope on the roof buses?

Question 16.
(a) Define momentum. Write its SI unit.
(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.

Question 17.
State any three changes that a force brings about on a body. Give one example of each.

Question 18.
Tabulate two differences between balanced and unbalanced forces. Write one example of each.
Question 19.
A book slides down a table top and comes to rest position after a certain distance. Name the force acting on the book. What types of forces are acting on the book? (Balanced/ unbalanced). Which force brought the book to rest?

Question 20..
The mud particles sticking on the rim of a bicycle wheel leave the rim of the wheel tangentially when it starts moving. Explain.

Question 21.
When a motor car makes a sharp turn at a high speed, we tend to get thrown to one side. Why?

Question 22..
What do you understand by inertia? Do all bodies have the same inertia? Illustrate giving an example.
Question 23..
State reason for the following:
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.

Question 11.
A stone of mass 1 kg is thrown with a velocity 20 m/s across the frozen surface of a lake and comes to rest after travelling a distance of 50 m. what is the force of friction between the stone and ice?

Question 12.
State Newton’s second law of motion and prove that Newton’s first law of motion is a special case of Newton’s second law of motion.
Question 13.
(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?
Question 14.
(i) Define momentum. Write its SI unit.
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/s2)
(iii) Explain how a karate player can break a pile of tiles with a single blow of his hand.

Question 15.
Do action and reaction act on the same body or on different bodies? Explain your answer with the help of example. How are they related in magnitude and direction? Write the total momentum of the gun and the bullet before firing.
Question 16.
State reason for the following:
a.A runner presses the ground with his feet before he starts his run.
b.To take the boat away from the bank of a river, the boat man pushes the bank with an oar.

Question 17.
Give an example to show that friction is an important factor in satisfying Newton’s third law of motion.
Question 18.
(a) State the law of conservation of momentum.
(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.

## Law of Conservation of Momentum Long answer type questions

Question 19.
(a) State law of conservation of momentum. Write SI unit of momentum.
(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?

Question 20.
(a) Define momentum. Write its SI unit.
(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.

Question 21.
Prove the law of conservation of momentum with clear explanation, diagram and equation.
Question 22.
(a) State law of conservation of momentum. Express it mathematically, when two bodies of masses $m_1$ and $m_2$ moving in same direction along same straight line with velocities $u_1$ and $u_2$ respectively, collide and their respective velocities after collision become $v_1$ and $v_2$.
(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.

Question 22.
Name and define the various types of inertia. Illustrate each of them with suitable example.

Question 23.
(i) Define momentum. State its SI unit.
(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.

Question 24
State the Law of Conservation of Momentum. Deduce this from Newton's second law of motion?

## Summary

This Extra questions on Force ,Momentum and Laws of Motion for Class 9 Physics is prepared keeping in mind the latest syllabus of CBSE . This has been designed in a way to improve the academic performance of the students. If you find mistakes , please do provide the feedback on the mail. 