Uniform Circular Motion

Question 1

When is a particle’s motion called uniform circular motion?

Answer 1

When the particle moves with a constant speed in a circular path

Question 2

What happens to the speed and direction in uniform circular motion?

Answer 2

The speed of the particle is uniform, because a particle in circular motion travels equal distances along the circular path in equal intervals of time. But the direction of motion of the particle changes at each point of the circular path.

Question 3

Why is the velocity of a particle in uniform circular motion variable?

Answer 3

This is because the speed of such a particle is uniform but the direction of motion of the particle goes through continuous changes at each point of the circular path. This implies that the velocity is non-uniform i.e., the motion is accelerated.

Question 4

How to find the direction of motion of a particle in uniform circular motion?

Answer 4

At any point, the direction of motion is along the tangent drawn at that point of the circular path.

Question 5

What is the difference between uniform circular motion and uniform linear motion?

Answer 5

In uniform linear motion, the speed and velocity, both are constant and therefore, acceleration is zero ; therefore, ULM is an unaccelerated motion, whereas in a uniform circular motion the velocity is variable (although the speed is uniform), so it is an acceleration motion.

Question 6

Under the influence of which force is the motion in circular path possible?

Answer 6

Centripetal force

Question 7

Give the meaning of centripetal

Answer 7

centre seeking

Question 8

Where is the centripetal force directed at each point of the circular path?

Answer 8

Towards the centre of the circle

Question 9

Define centripetal force

Answer 9

It is the force acting on a body moving in a circular path, in a direction towards the centre of the circular path

Question 10

From where is the required centripetal force obtained in an atom?

Answer 10

In an atom, an electron moves around the nucleus in a circular path for which the required centripetal force is obtained from the electrostatic force of attraction on the negatively charged electron by the positively charged nucleus

Question 11

From where is the required centripetal force obtained in a planet moving around the sun?

Answer 11

From the gravitational force of attraction on the planet by the Sun

Question 12

From where is the required centripetal force obtained in the Moon moving around the Earth?

Answer 12

The gravitational force of attraction on the Moon by Earth provides the required centripetal force

Question 13

From where is the required centripetal force obtained in a stone being whirled in a circular path?

Answer 13

The tension in the string provides the centripetal force

Question 14

In the absence of which force will a stone not turn to move in a circular path?

Answer 14

In the absence of tension

Question 15

Name a few instances where centripetal force is at play

Answer 15

1. In an atom, an electron moving around the nucleus
2. A plant moving around the sun
3. The Moon moving around the Earth
4. A stone being whirled around in a circular path

Question 16

When a body moves under the influence of centripetal force, which state of equilibrium is it in?

Answer 16

Dynamic equilibrium

Question 17

Under the influence of centripetal motion, a body has _ speed but _ acceleration as the _ keeps changing

Answer 17

uniform, variable, direction of motion

Question 18

Define centrifugal force

Answer 18

A force assumed (by an observer moving with the body) to be acting on the body in a direction away from the centre of circular oath

Question 19

Name the force which is not real, but fictitious

Answer 19

Centrifugal force

Question 20

Which factor is equal in centrifugal and centripetal force and which, different?

Answer 20

Their magnitude is the same, the direction opposite

Question 21

Why is the centrifugal force not the force of reaction of the centripetal force?

Answer 21

Because action and reaction do not act on the same body

Question 22

Why does a person standing outside a merry-go-round observe that the ball is moving in a circular path?

Answer 22

For the person standing on the ground, the ball moves in a circular path because the tension T in the string provides the centripetal force needed for the circular motion

Question 23

Why does the person standing on the platform of the merry-go-round observe the ball is stationary in front of him?

Answer 23

He considers the following 2 forces acting on the ball:-

1. the tension T of the string towards the centre of the
   merry-go-round
2. the centrifugal force away from the centre

The two forces are equal and opposite, therefore net force on ball is zero and it remains stationary

Question 24

The person standing on the platform of the MGR can only explain the stationary ball when he considers?

Answer 24

The centrifugal force along with the force of tension in the string

Question 25

If the string breaks of the rotating ball, what does the person at the platform of the MGR observe?

Answer 25

He will observe that the ball always remains in front of him moving radially away from him

Question 26

To what does the person at the platform attribute the motion of the ball moving radially away from him?

Answer 26

To the centrifugal force acting on the ball away from the centre

Question 27

If the string breaks of the rotating ball, what does the person on the ground observe?

Answer 27

That the ball is moving in a straight line along the tangent drawn at the position P of the ball on the circular path

Question 28

Describe fictitious force

Answer 28

A force that really does not exist, but is considered to describe (or understand) a certain motion

Question 29

Give another name for fictitious force

Answer 29

Virtual force

Question 30

Which force is real in the situation of the ball being tied at the end of a string tied to a MGR?

Answer 30

The force of tension in the string acting towards the centre (i.e., the centripetal force)