Physics

Rotational and Circular Motion

235 Questions

Rotational and circular motion examines the dynamics of objects moving in circular paths or rotating around an axis. Key concepts include angular momentum, torque, moment of inertia, and centripetal force. This is a highly scoring topic in the physics section of competitive exams.

Angular momentumCentripetal forceMoment of inertiaRolling objectsGyroscopic effect

Rotational and Circular Motion Questions

Multiple choice

The wheels are coned to prevent from rubbing the inside face of the rail head and to prevent lateral movement of the axle with its wheels. The slope of the cone is

  1. 1 in 5

  2. 1 in 20

  3. 1 in 10

  4. 1 in 15
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The standard coning slope for railway wheels is 1 in 20, which means for every 20 mm of horizontal distance, the tread rises 1 mm. This slight taper (approximately 2.86 degrees) helps maintain wheel centering, reduces flange contact, and improves ride quality. The 1 in 5 slope is too steep, while 1 in 10 and 1 in 15 are not standard values.

Multiple choice

In a case of uniform circular motion, the acceleration is

  1. zero

  2. constant in magnitude and directed radially inwards

  3. variable in magnitude, but constant in direction

  4. variable in magnituude, but tangential to the circle
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In uniform circular motion, the speed is constant but velocity continuously changes direction. This change in velocity toward the center creates centripetal acceleration - constant in magnitude (v²/r) and always directed radially inward toward the center of the circle.

Multiple choice

In case of uniform circular motion, the acceleration is

  1. zero

  2. constant in magnitude and directed radially inwards

  3. variable in magnitude

  4. variable in magnitude but tangential to the circle
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In case of uniform circular motion, the acceleration is constant in magnitude and it is directed radially inwards.

Multiple choice

The acceleration of a body moving in a circular path at uniform speed is

  1. directed away from the centre

  2. directed towards the centre

  3. directed tangentially

  4. zero
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In uniform circular motion, the velocity vector changes direction constantly. This change requires an acceleration directed toward the center of the circle, known as centripetal acceleration.

Multiple choice

Match the following ||| |---|---| |a. Translatory motion|1. It is the motion in which a body moves about a fixed axis without changing its position.| |b. Circular motion|2. It is the motion in which all the particles of a body move through the same distance in the same time. | |c. Periodic motion|3. It is the repetitive motion which repeats itself after a fixed interval of time. |

  1. a - 2, b - 3, c - 1

  2. a - 1, b - 2, c - 3

  3. a - 2, b - 1, c - 3

  4. a - 3, b - 1, c - 2

  5. a - 1, b - 3, c - 2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This is the correct option. Translatory motion is the motion in which all the particles of a body move through the same distance in the same time. Circular motion is the motion in which a body moves about a fixed axis without changing its position. Periodic motion is the repetitive motion which repeats itself after a fixed interval of time.

Multiple choice

Physicists most commonly call a mass moving in a straight line path as having:

  1. second order momentum

  2. translational momentum

  3. straight momentum

  4. angular or rotational momentum
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Translational momentum refers to the momentum of an object moving in a straight line. Angular momentum relates to rotational motion, and the other terms are not standard physics terminology for this concept.

Multiple choice

rad / sec is the unit for

  1. Angular displacement

  2. Angular velocity

  3. Angular acceleration

  4. Angular momentum
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

2      It is defined as the rate of change of angular displacement with respect to time. Angular velocity can be expressed in degrees per unit time (second, minute, hour, etc.), radians per unit time, or even revolutions per unit time.

Multiple choice

A stone which is tied to a thread is whirled in a circular path. As it revolves, the thread suddenly breaks. What happens then?

  1. The stone moves radially inward.

  2. The stone flies off tangentially.

  3. The stone moves radially outward.

  4. The stone falls straight down.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Yes, it is correct. The string exerts a force that continuously causes the stone to deviate from the straight line path the stone's inertia would cause it to follow. When the string caeses to exert that force, the stone continues along the tangential path that it currently is following.

Multiple choice

A mobile phone has a small motor with an eccentric mass used for vibrator mode. The location of the eccentric mass on motor with respect to the center of gravity (CG) of the mobile and the rest of the dimensions of the mobile phone are shown. The mobile is kept on a flat horizontal surface.

In addition, eccentric mass = 2 grams, eccentricty = 2.19 mm, mass of the mobile = 90 grams and g = 9.81 m/s2. Uniform speed (in RPM) of the motor for which the mobile will get just lifted off the ground at the end Q is approximately

  1. 3000

  2. 3500

  3. 4000

  4. 4500
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Correct Answer: 3500