Question:
State Newton's third law of motion.
Answer:
To every action there is an equal an opposite reaction.
Force and Laws of Motion
Q 1.
Are action-reaction forces simultaneous ?
Q 2.
While driving on a highway, an insect strikes on the car windshield and splatters. Which experiences greater impact (force): an insect or the windshield?
Q 3.
What is the unit of force in c.g.s system?
Q 4.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 5.
On what factor does inertia of a body depend ?
Q 6.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 7.
Can every force produce motion in every object?
Q 8.
Explain why a player lowers his hands while catching a cricket ball.
Q 9.
Can balanced forces change the shape and size of an object?
Q 10.
In the above question, which body is damaged more ?
Q 11.
Using second law of motion, derive the relation between force and acceleration.
Q 12.
An object of mass 1 kg travelling in a straight line with a velocity of 10 m/s collides with, and sticks to, a stationary wooden block of mass 5 kg. Then they both move off together in the
same straight line. Calculate the total momentum just before the impact and just after the impact. Also, calculate the velocity of the combined object.
Q 13.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
Q 14.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 15.
What acceleration is produced by a force of 5 N acting on a body of mass 20 kg ?
Q 16.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 17.
A car weighs 1500 kg.Its speed time graph is shown in Fig. Calculate the force required at the end of 5 seconds to bring the car to a stop within one second.
Q 18.
What is the SI unit of impulse.
Q 19.
A body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 20.
A man pushes a box of mass 50 kg with a force of 80 N. What will be the acceleration of the box due to this force? What would be the acceleration if the mass were doubled ?
Q 21.
A TV set is lying on a table. The TV set experiences a gravitational force (pull) downwards (FW) by the Earth. It also experiences a force on it due to table in contact i.e. (FTable-TV) in upward direction. Do these forces form an action-reaction pair? Do these forces follow Newton's third Law of motion?
Q 22.
What is formula of impulse?
Q 23.
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 ?
Q 24.
An object experiences a net zero external unbalanced force.Is it possible for the object to be travelling with a non-zero velocity ? If yes,state the conditions that must be placed on the magnitude and direction of the velocity.If no,provide a reason.
Q 25.
Name the unbalanced force that stops a ball rolling on the ground.
Q 26.
What is the net momentum of gun and bullet system before firing?
Q 27.
State Newton's First Law of motion.
Q 28.
If action is always equal to the reaction, explain how a horse can pull a cart.
Q 29.
Why does a bicycle slow down when the cyclist stop pedalling?
Q 30.
Suppose you were pushing on a heavy bucket of stones with 100 N of force and it did not move. How many newtons of force would be balancing the force that you were applying?
Q 31.
What is the momentum of a man of mass 75 kg when he walks with a velocity of 2 m/s ?
Q 32.
For how long should a force of 100 N act on a body of mass 20 kg so that it acquires a velocity of 100 m/s ?
Q 33.
Why does a gunman get a jerk on a firing a bullet ?
Q 34.
Explain what is meant by momentum of a body.Is it a scalar or a vector ? What are its units ?
Q 35.
Why do you fall in the forward direction when a moving bus brakes to a stop and fall backwards when it accelerates from rest?
Q 36.
What are non-contact forces? Give examples.
Q 37.
Identify the action and reaction forces in the following cases:
(a) A television (TV) lying on a table
(b) Pushing a wall with your hand
(c) Firing a bullet from a gun.
(d) Walking of a person on a ground.
Q 38.
Fill in the blanks :
The natural tendency of objects to resist a change in their state of rest or of uniform motion is called ______.
Q 39.
What are balanced forces?
Q 40.
Define 1 Newton force.
Q 41.
How is force related to acceleration produced in a body by its application?
Q 42.
What is the momentum of an object of mass m,moving with a velocity v ?(a)
(b)
(c)
(d) mv
Q 43.
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 ?
Q 44.
Can balanced forces move a body at rest ?
Q 45.
What are unbalanced forces ?
Q 46.
Do action-reaction forces act on the same body ?
Q 47.
State Newton’s third law of motion and principle of conservation of momentum.
Q 48.
An object experiences a net zero external unbalanced force. Is it possible for the object to be travelling with a non-zero velocity? If yes, state the conditions that must be placed on the magnitude and direction of the velocity. If no, provide a reason.
Q 49.
From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m/s. Calculate the initial recoil velocity of the rifle.
Q 50.
A hockey ball of mass 200 g travelling at 10 m s-1 is struck by a hockey stick so as to return it along its original path with a velocity at 5 m s-1. Calculate the change of momentum occurred in the motion of the hockey ball by the force applied by the hockey stick.
