Introduction
A force is a push or pull that can change the shape, speed, direction, or state of rest or motion of an object. Forces are responsible for all types of motion.
Effects of Force
- Change the speed of an object
- Change the direction of motion
- Change the shape or size of an object
- Start or stop motion
Types of Forces
1. Contact Forces
- Require physical contact.
Examples:
- Muscular force
- Frictional force
2. Non-Contact Forces
- Act without physical contact.
Examples:
- Gravitational force
- Magnetic force
- Electrostatic force
Balanced and Unbalanced Forces
| Balanced Forces | Unbalanced Forces |
|---|---|
| Net force is zero | Net force is not zero |
| No change in motion | Change in motion occurs |
| Object remains at rest or uniform motion | Object accelerates |
Newton’s Laws of Motion
First Law of Motion (Law of Inertia)
An object remains at rest or in uniform motion unless acted upon by an unbalanced force.
Inertia: Resistance to change in state of motion.
Second Law of Motion
The rate of change of momentum of an object is directly proportional to the applied force and occurs in the direction of the force.
Formula:F=ma
Where:
F = force
m = mass
a = acceleration
Third Law of Motion
For every action, there is an equal and opposite reaction.
Example:
Walking, swimming, rocket motion.
Momentum
- Product of mass and velocity.
- Formula:
Momentum=m×v
- Unit: kg m/s
Conservation of Momentum
In the absence of external force, the total momentum of a system remains constant.
Example:
Recoil of a gun, collision of objects.
Applications of Laws of Motion
- Seat belts in vehicles
- Catching a ball by moving hands backward
- Rocket propulsion
- Sports activities
Quick Short Q&A (Most Possible)
| Question | Short Answer |
|---|---|
| What is force? | Push or pull |
| SI unit of force? | Newton |
| Contact force example? | Friction |
| Non-contact force example? | Gravity |
| Balanced forces result? | No change in motion |
| Inertia means? | Resistance to change |
| Formula of force? | F = ma |
| Momentum formula? | m × v |
| Unit of momentum? | kg m/s |
| Newton’s third law? | Action–reaction |
| Momentum conserved when? | No external force |