Question 1

Question 1:
What name is given to the product of mass and velocity of a body?

Accepted Answer

Answer:
The product of mass and velocity of a body is called momentum.

Question 2

Question 2:
Name the physical quantity which is considered to be a measure of the quantity of motion of a body.

Accepted Answer

Answer:
Momentum is the physical quantity which is considered to be a measure of the quantity of motion of a body.

Question 3

Question 3:
What is the SI unit of momentum?

Accepted Answer

Answer:
The SI unit of momentum is kilogram meter per second (kg.m/s).

Question 4

Question 4:
State whether momentum is scalar or vector.

Accepted Answer

Answer:
Momentum is a vector quantity.

Question 5

Question 5:
What is the total momentum of the bullet and the gun before firing?

Accepted Answer

Answer:
The total momentum of the bullet and gun before it is fired  is zero.

Question 6

Question 6:
Name the physical quantity whose unit is kg.m/s.

Accepted Answer

Answer:
Momentum is the physical quantity whose unit is kg.m/s.

Question 7

Question 7:
What will be the momentum of a body of mass 'm' which is moving with a velocity 'v'?

Accepted Answer

Answer:
Momentum of a body of mass 'm' moving with a velocity 'v' =  m × v

Question 8

Question 8:
What is the usual name of the forces which cannot produce motion in a body but only change its shape?

Accepted Answer

Answer:
Balanced forces are the forces which cannot produce motion in a body but can change its shape.

Question 9

Question 9:
Name the unbalanced force which slow down a moving bicycle when we stop pedalling it.

Accepted Answer

Answer:
Friction is the unbalanced force which slows down a moving bicycle when we stop pedalling it.

Question 10

Question 10:
State whether the following statement is true or false :
Unbalanced forces acting on a body change its shape.

Accepted Answer

Answer:
False, unbalanced forces acting on a body changes its speed or its direction of motion, but does not change its shape.

Question 11

Question 11:
When a ball is dropped from a height, its speed increases gradually. Name the force which causes this change in speed.

Accepted Answer

Answer:
Gravity is the force which causes this change in the speed of the ball.

Question 12

Question 12:
Name the property of bodies (or objects) to resist a change in their state of rest or of motion.

Accepted Answer

Answer:
The property of bodies to resist a change in their state of rest or of motion is called inertia.

Question 13

Question 13:
What is the other name of Newton's first law of motion?

Accepted Answer

Answer:
‘Galileo’s law of inertia’ is the other name for Newton’s first law of motion.

Question 14

Question 14:
The mass of object A is 6 kg whereas that of another object B is 34 kg. Which of the two objects, A or B, has more inertia?

Accepted Answer

Answer:
Object B has more inertia because heavier objects have greater inertia than lighter objects.

Question 15

Question 15:
Name the scientist who gave the laws of motion.

Accepted Answer

Answer:
Sir Isaac Newton gave the laws of motion.

Question 16

Question 16:
State whether force is a scalar or a vector quantity.

Accepted Answer

Answer:
Force is a vector quantity.

Question 17

Question 17:
With which physical quantity should the speed of a running bull be multiplied so as to obtain its momentum?

Accepted Answer

Answer:
The speed of a running bull should be multiplied by the mass (of the bull) so as to obtain its momentum.

Question 18

Question 18:
Fill in the following blanks with suitable words :
(a) ____________ is a measure of the inertia of a body.
(b) When a running car stops suddenly, the passengers are jerked ____________.
(c) When a stationary car starts suddenly, the passengers are jerked ____________.
(d) Newton’s first law of motion is also called Galileo’s law of ____________.
(e) If there were no unbalanced force of ____________ and no ____________ resistance, a moving bicycle would go on moving forever.

Accepted Answer

Answer:
(a) Mass is a measure of the inertia of a body.
(b) When a running car stops suddenly, the passengers are jerked forward.
(c) When a stationary car starts suddenly, the passengers are jerked backward
(d) Newton’s first law of motion is also called Galileo’s law of inertia.
(e) If there were no unbalanced force of friction and no air resistance, a moving bicycle would go on moving forever.

Question 19

Question 19:
Explain why, it is easier to stop a tennis ball than a cricket ball moving with the same speed.

Accepted Answer

Answer:
It is easier to stop a tennis ball than a cricket ball moving with the same speed because it has less momentum than the cricket ball.

Question 20

Question 20:
Explain the meaning of the following equation :
p = m ✕ v
where symbols have their usual meanings.

Accepted Answer

Answer:
The given equation describes the momentum of a body as the product of its mass and velocity.
P = m × v
where, P = momentum
m = mass of the body
v = velocity of the body

Chapter 2 : Force and Laws of Motion