Friction and Circular Motion
A complete physics website covering friction, laws of friction, coefficient of friction, advantages and disadvantages of friction, circular motion, centripetal force, banking of roads, formulas, diagrams, solved examples, and exercises.
1. Friction
Friction is the force that opposes relative motion between two surfaces in contact.
2. Types of Friction
| Type | Description |
|---|---|
| Static Friction | Acts before motion starts |
| Sliding Friction | Acts during sliding motion |
| Rolling Friction | Acts during rolling motion |
| Fluid Friction | Acts in liquids and gases |
3. Laws of Friction
- Friction acts opposite to motion.
- Friction depends on nature of surfaces.
- Friction is proportional to normal reaction.
Where:
| Symbol | Meaning |
|---|---|
| F | Frictional force |
| μ | Coefficient of friction |
| N | Normal reaction |
Example
Find frictional force if coefficient of friction is 0.4 and normal reaction is 100 N.
F = 0.4 × 100
F = 40 N
4. Advantages and Disadvantages of Friction
| Advantages | Disadvantages |
|---|---|
| Helps walking | Produces heat |
| Helps writing | Causes wear and tear |
| Helps vehicles move | Reduces efficiency |
5. Circular Motion
Motion of an object along a circular path is called circular motion.
6. Centripetal Force
The force acting towards the center of the circular path is called centripetal force.
Where:
| Symbol | Meaning |
|---|---|
| m | Mass |
| v | Velocity |
| r | Radius of circular path |
Solved Problem
Find centripetal force if m = 2 kg, v = 4 m/s, r = 2 m.
F = 2 × 4² / 2
F = 2 × 16 / 2
F = 16 N
7. Banking of Roads
Roads are tilted at curves to reduce the risk of skidding and provide necessary centripetal force.
8. Practice Exercises
Short Questions
- Define friction.
- Write types of friction.
- Define circular motion.
- What is centripetal force?
- Why are roads banked?
Numerical Problems
- Find frictional force if μ = 0.5 and N = 60 N.
- Calculate centripetal force for m = 5 kg, v = 6 m/s, r = 3 m.
- A body moves in circular path of radius 4 m with speed 8 m/s. Find centripetal force if mass is 2 kg.
9. Formula Summary
| Topic | Formula |
|---|---|
| Friction | F = μN |
| Centripetal Force | F = mv²/r |