SSC CGL Physics · Kinematics and Motion
Kinds of Motion and Rotation
Kinds of motion with an example of each, centripetal acceleration, and how angular velocity and moment of inertia behave in a rigid body.
Why this matters
Five questions in the bank: one from the 2023 shifts and two each from the 2024 and 2025 shifts. Each tests one definition, so the two tables answer them.
Concept 1 of 2: Kinds of motion
Definition
The kinds:
- Translatory: the whole body moves along a line, as a falling ball.
- Rotatory: turning about an axis, as fan blades.
- Periodic: repeating at fixed intervals, as clock hands or the Earth round the Sun.
- Oscillatory: to and fro about a mean position, as a pendulum.
- Curvilinear: along a curved path, as a thrown javelin. Rectilinear is along a straight line.
| Kind | Example |
|---|---|
| Rotatory | Fan blades |
| Periodic | Earth round the Sun |
| Oscillatory | Pendulum |
| Curvilinear | Thrown javelinQ |
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 1 · Kinematics and Motion · Kinds of Motion and Rotation
An orbit is not oscillation
Concept 2 of 2: Circular motion and rotation
Definition
The facts:
- Centripetal acceleration a = v squared / R, where v is the speed along the circle.
- In a rigid body every particle has the same angular velocity; linear speed v = (angular velocity) x r grows with distance.
- Moment of inertia I = sum of m r squared: a scalar that depends on the axis.
Practise this conceptself-check · 3 quick reps
The same idea in a real exam question:
Example 2 · Kinematics and Motion · Kinds of Motion and Rotation
Same angle, different speed
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Reference tables (2)
Kinds of motion4 rows
| Kind | Example |
|---|---|
| Rotatory | Fan blades |
| Periodic | Earth round the Sun |
| Oscillatory | Pendulum |
| Curvilinear | Thrown javelinQ |
Watch out for (2)
- An orbit is not oscillation→ Kinds of motion
- Same angle, different speed→ Circular motion and rotation
Test yourself on a real paper
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