FORCE AND ITS TYPES
Complete Notes for Competitive Examinations
By Home Academy
1. Introduction to Force
Force is a push or pull acting on an object that changes or tries to change its state of rest, motion, or shape.
Definition
A force is an external agent capable of changing:
State of rest
State of motionDirection of motion
Shape and size of an object
2. SI Unit and Formula of Force
| Quantity | Symbol | SI Unit |
|---|---|---|
| Force | F | Newton (N) |
| Mass | m | Kilogram (kg) |
| Acceleration | a | m/s² |
Newton’s Second Law
F = ma
Where:
F = Force
m = Mass
a = Acceleration
3. Characteristics of Force
| Characteristic | Description |
|---|---|
| Magnitude | Size of force |
| Direction | Direction in which force acts |
| Point of Application | Point where force acts |
| Nature | Push or pull |
4. Effects of Force
Force can:
Move a stationary object
Stop a moving object
Change speed
Change direction
Change shape or size
5. Types of Force
Force is mainly divided into:
| Main Type | Subtypes |
|---|---|
| Contact Force | Muscular force, Frictional force |
| Non-Contact Force | Gravitational, Magnetic, Electrostatic |
6. Contact Forces
A. Muscular Force
Force produced by muscles of humans or animals.
Examples
Pulling a cart
Lifting a bagImportant Points
It is a contact force.
Requires physical contact.B. Frictional Force
Force that opposes motion between two surfaces in contact.
Types of Friction
| Type | Description |
|---|---|
| Static Friction | Acts on stationary objects |
| Sliding Friction | Acts when surfaces slide |
| Rolling Friction | Acts during rolling |
| Fluid Friction | Resistance by liquids/gases |
Important Points
Friction always opposes motion.
Rolling friction is minimum.Useful for walking and braking.
7. Non-Contact Forces
A. Gravitational Force
Force of attraction between two masses.
Example
Earth attracts objects toward itself.Important Points
Universal force
Depends on mass and distanceB. Magnetic Force
Force exerted by magnets.
Important Points
Like poles repel
Unlike poles attractC. Electrostatic Force
Force between electrically charged particles.
Important Points
Opposite charges attract
Similar charges repel8. Balanced and Unbalanced Forces
| Balanced Force | Unbalanced Force |
|---|---|
| Net force = 0 | Net force ≠ 0 |
| No change in motion | Changes motion |
| Object remains at rest or uniform motion | Produces acceleration |
9. Newton’s Laws of Motion
First Law
An object remains at rest or in uniform motion unless acted upon by an external force.
Also Called
Law of Inertia
Second Law
Force is equal to mass × acceleration.
F = ma
Third Law
Every action has an equal and opposite reaction.
Example
Recoil of gun
Rocket propulsion
10. Inertia
Property of matter to resist changes in motion.
Types of Inertia
| Type | Example |
|---|---|
| Inertia of Rest | Passenger falls backward |
| Inertia of Motion | Passenger falls forward |
| Inertia of Direction | Stone tied to string |
11. Momentum
Product of mass and velocity.
p = mv
Where:
p = Momentum
m = Massv = Velocity
12. Centripetal Force
Force acting toward the center of a circular path.
Examples
Satellites around Earth
Stone tied to string13. Important Differences
Mass vs Weight
| Mass | Weight |
|---|---|
| Amount of matter | Force of gravity |
| Constant everywhere | Changes with gravity |
| Unit = kg | Unit = Newton |
Contact vs Non-Contact Force
| Contact Force | Non-Contact Force |
|---|---|
| Requires contact | No physical contact |
| Example: Friction | Example: Gravity |
14. Important Exam Points
SI unit of force = Newton
CGS unit = Dyne1 Newton = 10⁵ dyne
Force is a vector quantity.
Friction opposes motion.
Balanced force does not change motion.
Newton discovered gravitational law.
Rolling friction is least.
15. Most Important MCQs
Multiple Choice Questions
1. SI unit of force is:
A. Joule
B. Newton
C. Watt
D. Pascal
✅ Answer: B
2. Which force acts without contact?
A. Friction
B. Muscular
C. Magnetic
D. Mechanical
✅ Answer: C
3. Friction always:
A. Helps motion
B. Opposes motion
C. Increases speed
D. Changes mass
✅ Answer: B
4. Which friction is minimum?
A. Static
B. Sliding
C. Rolling
D. Fluid
✅ Answer: C
5. Force is a:
A. Scalar quantity
B. Vector quantity
C. Unit quantity
D. Derived quantity
✅ Answer: B
6. Newton’s first law is also called:
A. Law of gravity
B. Law of momentum
C. Law of inertia
D. Law of force
✅ Answer: C
7. Equal and opposite reaction represents:
A. First law
B. Second law
C. Third law
D. Gravitation law
✅ Answer: C
8. Momentum depends upon:
A. Mass only
B. Velocity only
C. Mass and velocity
D. Weight and speed
✅ Answer: C
16. Statement-Based Conceptual Questions
Question 1
Consider the following statements regarding friction:
Friction always opposes relative motion.
Rolling friction is greater than sliding friction.
Friction helps us to walk properly.
Choose the correct option:
A. Only 1 and 2
B. Only 1 and 3
C. Only 2 and 3
D. 1, 2 and 3
✅ Answer: B
Explanation
Statement 1 → Correct
Statement 2 → Incorrect (rolling friction is least)
Statement 3 → Correct
Question 2
Consider the following statements:
Balanced forces can change shape of object.
Balanced forces always produce acceleration.
Unbalanced forces change state of motion.
A. Only 1 and 3
B. Only 2 and 3
C. Only 1
D. Only 3
✅ Answer: A
Question 3
Which of the following are non-contact forces?
Gravitational force
Magnetic force
Muscular force
Electrostatic force
A. 1, 2 and 4 only
B. 1 and 3 only
C. 2 and 3 only
D. 1, 2, 3 and 4
✅ Answer: A
Question 4
Consider the following statements regarding Newton’s laws:
First law explains inertia.
Second law gives relation between force and acceleration.
Third law explains conservation of energy.
A. Only 1 and 2
B. Only 2 and 3
C. Only 1 and 3
D. 1, 2 and 3
✅ Answer: A
17. Previous Exam Type Questions
1. Which scientist proposed the law of gravitation?
A. Galileo
B. Newton
C. Einstein
D. Kepler
✅ Answer: B
2. A passenger in a moving bus falls forward when brakes are suddenly applied due to:
A. Momentum
B. Friction
C. Inertia of motion
D. Gravitation
✅ Answer: C
3. Which quantity has both magnitude and direction?
A. Work
B. Energy
C. Force
D. Power
✅ Answer: C
18. Quick Revision Points
Force = Push or Pull
Unit = Newton
Force is vector quantity
Friction opposes motion
Gravity is non-contact force
Action and reaction are equal and opposite
Balanced force → no acceleration
Unbalanced force → acceleration produced
Momentum = mass × velocity
Inertia resists change in motion
19. One-Liner Questions for Revision
| Question | Answer |
|---|---|
| SI unit of force | Newton |
| CGS unit of force | Dyne |
| Scientist of gravitation | Newton |
| Force responsible for falling objects | Gravity |
| Lowest friction | Rolling friction |
| Property resisting change | Inertia |
| Formula of momentum | p = mv |
20. Practice Assertion–Reason Questions
Assertion (A)
Force is a vector quantity.
Reason (R)
Force has both magnitude and direction.
A. Both A and R are true and R explains A
B. Both true but R not explanation
C. A true, R false
D. A false, R true
✅ Answer: A
Assertion (A)
Rolling friction is greater than sliding friction.
Reason (R)
Rolling bodies experience less surface resistance.
A. Both true
B. A true, R false
C. A false, R true
D. Both false
✅ Answer: C
Conclusion
Force is one of the most fundamental concepts in physics. Questions from force, Newton’s laws, friction, gravitation, and momentum are frequently asked in competitive exams such as SSC, JKSSB, Railway, UGC NET, and State Exams. Understanding conceptual differences and statement-based questions is very important for scoring high marks.
Prepared By Home Academy