ANAND CLASSES study material and Notes explore the key differences between circular and rotatory motion with definitions, examples, MCQs, conceptual questions, and quick revision notes. Ideal for JEE, NEET, and CBSE Class 11 Physics preparation.
Difference Between Circular Motion and Rotatory Motion
| Feature | Circular Motion | Rotatory Motion |
|---|---|---|
| Definition | Motion of an object along a circular path. | Motion of an object about its own axis. |
| Path | A fixed circular path. | Rotation around an internal axis. |
| Example | A car moving on a circular track, the revolution of Earth around the Sun. | A spinning top, the rotation of Earth on its own axis. |
| Nature | The entire object moves along a circle. | Different points of the object follow different circular paths around the axis. |
| Fixed Axis? | May or may not have a fixed axis. | Always has a fixed axis within the object. |
| Force Required | Centripetal force keeps the object in circular motion. | Internal forces maintain rotational motion. |
Key Points:
- Circular motion can be of a point object or an extended object moving in a circle.
- Rotatory motion is when an extended body spins around its own axis.
MCQs on Circular and Rotatory Motion
1. Which of the following is an example of circular motion?
a) A rotating fan blade
b) The Moon revolving around the Earth
c) A spinning top
d) A rolling ball
✔ Answer: b) The Moon revolving around the Earth
2. In which type of motion does an object move along a circular path?
a) Rectilinear Motion
b) Translatory Motion
c) Circular Motion
d) Oscillatory Motion
✔ Answer: c) Circular Motion
3. What is the main difference between circular and rotatory motion?
a) Circular motion happens along a straight path, rotatory motion happens in a curve
b) Circular motion involves the entire object moving in a circle, while rotatory motion involves spinning around an axis
c) Circular motion needs no external force, rotatory motion does
d) Circular motion is always fast, rotatory motion is slow
✔ Answer: b) Circular motion involves the entire object moving in a circle, while rotatory motion involves spinning around an axis
4. The motion of a ceiling fan is an example of:
a) Circular motion
b) Rotatory motion
c) Rectilinear motion
d) Oscillatory motion
✔ Answer: b) Rotatory motion
5. Which of the following has both circular and rotatory motion?
a) A bicycle wheel moving on a straight road
b) A ball thrown upwards
c) A stationary spinning top
d) A pendulum
✔ Answer: a) A bicycle wheel moving on a straight road
Conceptual Questions with Answers
Q1. Define circular motion with an example.
Ans: Circular motion is the motion of an object along a circular path. Example: A satellite orbiting Earth.
Q2. What is rotatory motion? Give an example.
Ans: Rotatory motion occurs when a body spins around a fixed axis. Example: A spinning top.
Q3. Differentiate between circular and rotatory motion.
Ans:
- Circular Motion: The whole object moves in a circular path (e.g., a car moving on a circular track).
- Rotatory Motion: The object rotates about its own axis (e.g., a fan blade spinning).
Q4. Does a rotating Earth exhibit circular or rotatory motion? Explain.
Ans: The Earth exhibits both:
- Rotatory Motion: It spins around its own axis.
- Circular Motion: It revolves around the Sun in an orbit.
Q5. Can an object have both circular and rotatory motion simultaneously? Give an example.
Ans: Yes, a rolling wheel has both circular (center moves in a circular path) and rotatory (spins around its own axis) motion.
Quick Revision Notes
✔ Circular Motion: Object moves in a circular path (e.g., a satellite orbiting Earth).
✔ Rotatory Motion: Object spins around its own axis (e.g., a spinning top).
✔ Circular motion may not need a fixed axis, but rotatory motion always has one.
✔ A bicycle wheel moving forward has both circular and rotatory motion.
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