### Question:

What is collision? What are the types of collision?

#### Answer:

The interaction between two or more bodies causing the exchange of momentum is called

collision. It is categorised as of two types:

- elastic collision (both momentum and kinetic energy are conserved)
- inelastic collision (only momentum is conserved)

### Force and Laws of Motion

#### Q 1.

A stone of 1 kg is thrown with a velocity if 20

$ms-1$ 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 ?

#### Q 2.

What is force ? What is inertia ? How is inertia measured ?

#### Q 3.

Why does a gun recoil on firing ? Obtain an expression for recoil velocity of gun.

#### Q 4.

A bullet of mass 10 g travelling horizontally with a velocity of 150 m/s strikes a stationary wooden block and comes to rest in 0.03 s. Calculate the distance of penetration of the bullet into the block. Also calculate the magnitude of the force exerted by the wooden block on the bullet.

#### Q 5.

Fill in the blanks :

When a car enters a curved path, the person sitting in it is thrown outwards. This is because of the property of ______________.

#### Q 6.

Which would require a greater force : accelerating a 2 kg mass at 5

$m/s2$ or a 4 kg mass at 2

$m/s2$ ?

#### Q 7.

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 8.

Derive the unit of force using the second law of motion. A force of 5 N produces an acceleration of

$8\; m\; s-2$ on a mass

$m$_{1} and an acceleration of 24

$m\; s-2$ on a mass

$m$_{2}.What acceleration would the same force provide if both the masses are tied together ?

#### Q 9.

State Newton’s first law of motion. Hence define force and inertia.

#### Q 10.

Fill in the blanks :

It is dangerous to jump out of a moving bus because due to _________ one falls forward.

#### Q 11.

A force of 5 N gives a mass

$m$_{1} an acceleration of 10

$m/s2$,and a mass

$m$_{2},an acceleration of 20

$m/s2$.What acceleration would it give if both the masses were tied together ?

#### Q 12.

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 13.

A hockey ball of mass 200 g travelling at 10 m/s is struck by a hockey stick so as to return it along its original path with a velocity of 5 m/s.Calculate the change in momentum of the hockey ball by the force applied by the hockey stick.

#### Q 14.

What is the SI unit of force ?

#### Q 15.

What are balanced forces ?

#### Q 16.

Can balanced forces move a body at rest ?

#### Q 17.

What are unbalanced forces ?

#### Q 18.

Name the three types of inertia.

#### Q 19.

Define momentum of a body.

#### Q 20.

Derive the relation F = ma,where the symbols have their usual meanings.

#### Q 21.

Why is it advised to tie any luggage kept on the roof of a bus with a rope?

#### Q 22.

A truck starts from rest and rolls down a hill with a constant acceleration. It travels a distance of 400 m in 20 s. Find its acceleration. Find the force acting on it if its mass is 7 metric tonnes. (Hint: 1 metric tonne = 1000 kg.)

#### Q 23.

Using a horizontal force of 200 N, we intend to move a wooden cabinet across a floor at a constant velocity. What is the friction force that will be exerted on the cabinet?

#### Q 24.

Fill in the blanks :

When we shake a branch of a mango tree the mangoes fell down, this happens because of ___________.

#### Q 25.

Fill in the blanks :

A cyclist on a levelled road does not come to rest immediately even he stops pedalling. It is due to ______________.

#### Q 26.

A man pushes a box of mass 50 kg with a force of 80 N.What will be the acceleration of the box ? What would be the acceleration if the mass were halved ?

#### Q 27.

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

$m/s2$ ?

#### Q 28.

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 29.

Do action-reaction forces act on the same body ?

#### Q 30.

A person in a bus tends to fall backwards, when it starts suddenly ?

#### Q 31.

State and explain Newton’s third law of motion.How will you prove it experimentally ?

#### Q 32.

State Newton's First Law of motion.

#### Q 33.

If the set of forces acting on an object are balanced, then object

(a) must be at rest.

(b) must be moving

(c) must not be accelerating.

(d) none of these.

#### Q 34.

**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 35.

Fill in the blanks :

The ______ of an object is a measure of its inertia.

#### Q 36.

Give an example that force can make a stationary body move.

#### Q 37.

What are unbalanced forces?

#### Q 38.

Define 1 Newton force.

#### Q 39.

When a force acting on a body has equal and opposite reaction, then why should the body move at all?

#### Q 40.

What would be the force required to produce an acceleration of 2

$m/s2$ in a body of mass 12 kg ? What would be the acceleration if the force were doubled ?

#### Q 41.

A constant force acts on an object of mass 5 kg for a duration of 2 s.It increases the object’s velocity from 3 m/s to 7 m/s.Find the magnitude of the applied force. Now if the force were applied for a duration of 5 s,what would be the final velocity of the object ?

#### Q 43.

State Newton’s second law of motion and establish that F = ma where symbols have their usual meanings.

#### Q 44.

Explain briefly any three applications of Newton’s third law of motion.

#### Q 45.

Honey and Sunny are two friends.Both are financially well off.Honey is fond of driving an SUV while Sunny enjoys driving Tata Nano.Honey explains to Sunny the risks of driving a light vehicle and Sunny explains to Honey the cost factor.

Read the above passage and answer the following questions :

(i) With whom do you agree,with Honey or with Sunny?

(ii) Explain, why?

(iii) Which values of life do you learn from this discussion?

#### Q 46.

When a carpet is beaten with a stick, dust comes out of it. Explain.

#### Q 47.

What are non-contact forces? Give examples.

#### Q 48.

Define 1N (Newton).

#### Q 49.

Are there any limitations to Newton's Laws of motion?

#### Q 50.

Fill in the blanks :

An umbrella protects us from rain it is based on the property of _____________.