Question:
It is easier to stop a tennis ball than a cricket ball moving with the same speed. Why ?
Answer:
This is because tennis ball is lighter than the cricket ball. It has a smaller momentum and hence smaller force is required to stop the tennis ball.
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.
Do action-reaction forces produce the same magnitude of acceleration ?
Q 4.
On what factor does inertia of a body depend ?
Q 5.
Explain why a player lowers his hands while catching a cricket ball.
Q 6.
Can every force produce motion in every object?
Q 7.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
Q 8.
What is the SI unit of impulse.
Q 9.
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 10.
Fill in the blanks :
The study of motion of a body under the action of a force is called ______.
Q 11.
When a branch of a tree is shaken, some of the fruits may fall down.Why ?
Q 12.
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 13.
Can balanced forces change the shape and size of an object?
Q 14.
A body of mass 25 kg has momentum of 125 kg m/s. What is the velocity of the body?
Q 15.
What is the net momentum of gun and bullet system before firing?
Q 16.
The masses of two objects are 2 kg and 20 kg. Which has greater inertia ?
Q 17.
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 18.
In the above question, which body is damaged more ?
Q 19.
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 20.
Using second law of motion, derive the relation between force and acceleration.
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.
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.
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 24.
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 25.
Name the physical quantity that corresponds to the rate of change of momentum.
Q 26.
Name the unbalanced force that stops a ball rolling on the ground.
Q 27.
Why does a gunman get a jerk on a firing a bullet ?
Q 28.
What acceleration is produced by a force of 5 N acting on a body of mass 20 kg ?
Q 29.
Why is the person hurt less when he falls on a spongy surface?
Q 30.
What is formula of impulse?
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 32.
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 33.
What is the total momentum of the bullet and the gun on firing ?
Q 34.
Why does a gun recoil on firing ? Obtain an expression for recoil velocity of gun.
Q 35.
State Newton’s first law of motion. Hence define force and inertia.
Q 37.
State why Newton's first law of motion is called law of inertia.
Q 38.
What are balanced and unbalanced forces?
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.
Fill in the blanks :
The ______ of an object is a measure of its inertia.
Q 41.
Fill in the blanks :
When we shake a branch of a mango tree the mangoes fell down, this happens because of ___________.
Q 42.
Fill in the blanks :
________ is the tendency of an object to resist a change in motion.
Q 43.
Why does a bicycle slow down when the cyclist stop pedalling?
Q 44.
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 45.
A body of mass 1 kg is kept at rest.A constant force of 6-0 N starts acting on it.Find the time taken by the body to move through a distance of 12 m.
Q 46.
Two hockey players of opposite teams,while trying to.hit a hockey ball on the ground collide and immediately become entangled.One has a mass of 60 kg,and was moving with a velocity 5.0 m/s,while the other has a mass of 55 kg and was moving faster with a velocity of 6.0 m/s towards the first player,In which direction and with what velocity will they move after they become entangled ? Assume that the frictional force acting between the feet of the two players and ground is negligible.
Q 47.
Name the three types of inertia.
Q 48.
A person in a bus tends to fall backwards, when it starts suddenly ?
Q 49.
Name any two applications of the law of conservation of linear momentum.
Q 50.
Show that kg-
and N-s represent the same quantity.Which is that quantity ?
