Question

Complete the sentences and explain them.

a. The minimum distance between the start and finish points of the motion of an object is called the ........... of the object.

b. Deceleration is -------- acceleration.

c. When an object is in uniform circular motion, its ......... changes at every point.

d. During collision ........... remains constant.

e. The working of a rocket depends on Newton’s ........ law of motion.

Answer 1

a. The minimum distance between the start and finish points of the motion of an object is called the displacement of the object.
The shortest distance between the initial and final position of an object is displacement.

b. Deceleration is negative acceleration.
When a body is decelerating, it means its speed is decreasing speed. An acceleration with a negative also shows that the speed of the body is decreasing.

c. When an object is in uniform circular motion, its velocity changes at every point.
In a uniform circular motion, the direction of motion of the body changes at every instant of time. This continuous change in the direction of motion of the body at every instant accounts for the change in its velocity at every point ot instant.

d. During collision momentum of the system remains constant.
When two bodies collide with each other as shown, action and reaction force comes into action i.e. two bodies exerts force on each other.

Now, momentum of the ball system is given as:

Before collision: m₁u₁ + m₂u₂

After collision: m₁v₁ + m₂v₂

Rate of change of momentum of ball 1 is given as:

Where, t → Collision time

Rate of change of momentum of ball 2 is given as:

Using Newton’s third law of motion, we can relate the forces F₁₂ and F₂₁ as:

F₁₂ = −F₂₁

∴ Momentum of the system before collision = Momentum of the system after collision

e. The working of a rocket depends on Newton’s third law of motion.

The burning fuel inside the rocket creates a forward push on the rocket. This forward push creates an equal and opposite push on the exhaust gases. Thus, the working of a rocket depends on Newton’s third law of motion.