Question:
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?
Answer:
100N but in opposite direction to our pushing force.
Force and Laws of Motion
Q 1.
Are action-reaction forces simultaneous ?
Q 2.
Can every force produce motion in every object?
Q 3.
What is the unit of force in c.g.s system?
Q 4.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 5.
On what factor does inertia of a body depend ?
Q 6.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 7.
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 8.
Explain why a player lowers his hands while catching a cricket ball.
Q 9.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 10.
What is the SI unit of impulse.
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.
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 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.
In the above question, which body is damaged more ?
Q 17.
Using second law of motion, derive the relation between force and acceleration.
Q 18.
A body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 19.
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 20.
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 21.
What acceleration is produced by a force of 5 N acting on a body of mass 20 kg ?
Q 22.
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 23.
Why does a gunman get a jerk on a firing a bullet ?
Q 24.
What is the net momentum of gun and bullet system before firing?
Q 25.
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 26.
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 27.
What is formula of impulse?
Q 28.
Name the unbalanced force that stops a ball rolling on the ground.
Q 29.
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 30.
Why does a bicycle slow down when the cyclist stop pedalling?
Q 31.
A certain force exerted for 1 -2 s raises the speed of an object from 1.8 m/s to 4.2 m/s. Later,the same force is applied for 2 second. How much does the speed change in 2 s ?
Q 33.
If action is always equal to the reaction, explain how a horse can pull a cart.
Q 34.
Write the SI and CGS unit of force.
Q 35.
What is the momentum of an object of mass m,moving with a velocity v ?(a)
(b)
(c)
(d) mv
Q 36.
State the law of conservation of linear momentum.
Q 37.
Explain what is meant by momentum of a body.Is it a scalar or a vector ? What are its units ?
Q 38.
State why Newton's first law of motion is called law of inertia.
Q 39.
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 40.
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 41.
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 42.
Fill in the blanks :
________ is the tendency of an object to resist a change in motion.
Q 43.
If the body is found to be accelerated, is the force acting on it balanced or unbalanced?
Q 44.
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 46.
Two objects of masses 100 g and 200 g are moving along the same line in the same direction with velocities of 2 m/s and 1 m/s,respectively.They collide and after the collision, the first object moves at a velocity of 1.67 m/s in the same direction.Determine the velocity of the second object
Q 47.
An automobile vehicle has a mass of 1500 kg.What must be the force between the vehicle and road if the vehicle is to be stopped with a negative acceleration of 1.7
?
Q 48.
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 49.
What is the SI unit of force ?
Q 50.
Can balanced forces stop a moving body ?
