Laws of motion

[Verse 1]

📚 LAWS OF MOTION — NOTES

1. Force

Force is a push or pull which can change the state of rest or motion of an object.

SI unit: Newton (N)

Effects of force

It can make a stationary object move.

It can stop a moving object.

It can change the speed of an object.

It can change the direction of motion.

It can change the shape of an object.


[Verse 2]

2. Balanced and Unbalanced Forces

Balanced forces

When two or more forces acting on an object are equal and opposite, they are called balanced forces.

Net force = 0

Unbalanced forces

When the forces acting on an object are not equal, they are called unbalanced forces.

They can change the motion of an object.


[Verse 3]

3. Inertia

Inertia is the tendency of an object to resist any change in its state of rest or motion.

Types of inertia

1. Inertia of Rest

An object at rest tends to remain at rest.

Example: When a bus starts suddenly, passengers tend to fall backwards.

2. Inertia of Motion

A moving object tends to remain in motion.

Example: When a moving bus stops suddenly, passengers tend to move forward.

3. Inertia of Direction

An object tends to continue moving in the same direction.

Example: Passengers are pushed sideways when a bus takes a sharp turn.

Greater the mass → greater the inertia.


[Verse 4]

4. Newton's First Law

Statement:

An object remains at rest or continues to move with uniform velocity in a straight line unless an external unbalanced force acts on it.

It is also called the Law of Inertia.


[Verse 5]

5. Momentum

Momentum is the quantity of motion possessed by a moving object.

Formula:

p = mv

Where:

p = momentum

m = mass

v = velocity

SI unit: kg m/s

Greater mass or greater velocity means greater momentum.


[Verse 6]

6. Newton's Second Law

Statement:

The rate of change of momentum of an object is directly proportional to the applied force and takes place in the direction of the force.

For a body of constant mass:

F = ma

Where:

F = force

m = mass

a = acceleration

SI unit of force = Newton (N)

1 Newton

1 N is the force required to produce an acceleration of 1 m/s² in a body of mass 1 kg.

1 N = 1 kg m/s²


[Verse 7]

7. Newton's Third Law

Statement:

For every action, there is an equal and opposite reaction.

Examples:

Walking

Swimming

Rowing a boat

Rocket propulsion

Recoil of a gun

Action and reaction:

Are equal in magnitude.

Are opposite in direction.

Act on different objects.


[Verse 8]

8. Conservation of Momentum

When no external unbalanced force acts on a system, the total momentum of the system remains constant.

Formula:

Total momentum before collision = Total momentum after collision


[Outro]

IMPORTANT FORMULAS

Quantity

Formula

SI Unit

Momentum

p = mv

kg m/s

Force

F = ma

N

Acceleration

a = F/m

m/s²

Newton

1 N = 1 kg m/s²