Question:
What acceleration is produced by a force of 5 N acting on a body of mass 20 kg ?
Answer:
Here,F = 5 N, m = 20 kg, a = ?
From F = ma, a = ==0.25
Force and Laws of Motion
Q 1.
Are action-reaction forces simultaneous ?
Q 2.
What is the unit of force in c.g.s system?
Q 3.
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 4.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 5.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 6.
Can every force produce motion in every object?
Q 7.
On what factor does inertia of a body depend ?
Q 8.
Explain why a player lowers his hands while catching a cricket ball.
Q 9.
In the above question, which body is damaged more ?
Q 10.
Using second law of motion, derive the relation between force and acceleration.
Q 11.
Can balanced forces change the shape and size of an object?
Q 12.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
Q 13.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 14.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 15.
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 16.
What is the SI unit of impulse.
Q 17.
What acceleration is produced by a force of 5 N acting on a body of mass 20 kg ?
Q 18.
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 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 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 22.
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 23.
What is formula of impulse?
Q 24.
Why does a gunman get a jerk on a firing a bullet ?
Q 25.
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 26.
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 27.
Name the unbalanced force that stops a ball rolling on the ground.
Q 28.
Explain what is meant by momentum of a body.Is it a scalar or a vector ? What are its units ?
Q 29.
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 30.
What is the net momentum of gun and bullet system before firing?
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.
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 33.
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.
Q 34.
What do you mean by a resultant force?
Q 35.
How is force related to acceleration produced in a body by its application?
Q 36.
The following is the distance-time table of an object in motion :
| Time(s) | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
|---|
|
| Distance (m) | 0 | 1 | 8 | 27 | 64 | 125 | 216 | 343 |
|---|
(a) What conclusion can you draw about the acceleration ? Is it constant ? increasing ? decreasing ?zero ?
(b) What do you infer about the forces acting on the object ?
Q 37.
Can balanced forces move a body at rest ?
Q 38.
State Newton’s third law of motion and principle of conservation of momentum.
Q 39.
Establish relation between inertia and mass.
Q 40.
Why is it easier to stop a tennis ball in comparison to a cricket ball moving with the same speed ?
Q 41.
Name the categories of forces based on interaction.
Q 42.
What are contact forces? Give examples
Q 43.
A stone of 1 kg is thrown with a velocity of 20 m s-1 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 the ice? (Calculate time taken and acceleration also).
Q 44.
If action is always equal to the reaction, explain how a horse can pull a cart.
Q 45.
According to the third law of motion when we push on an object, the object pushes back on us with an equal and opposite force. If the object is a massive truck parked along the road side, it will probably not move. A student justifies this by answering that the two opposite and equal forces cancel each other. Comment on this logic and explain why the truck does not move.
Q 46.
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 47.
A motorcar of mass 1200 kg is moving along a straight line with a uniform velocity of 90 km/h. Its velocity is slowed down to 18 km/h in 4 s by an unbalanced external force. Calculate the acceleration and change in momentum. Also calculate the magnitude of the force required.
Q 48.
Fill in the blanks :
The momentum of an object is the product of its _____ and _______ and has the same direction as that of the ________.
Q 49.
Fill in the blanks :
When a passenger jumps out of moving bus, he falls down. It is due to _______________.
Q 50.
Fill in the blanks :
When the playing card is flicked with the finger the coin placed over it falls in the tumbler. It is due to ____________.
