🍎 Laws of Motion

1. Newton's First Law (Law of Inertia)

Every body continues to be in its state of rest or of uniform motion in a straight line unless compelled by some external unbalanced force.

🛑 Inertia

The inherent property of a material body to resist any change in its state of rest or motion. Mass is the measure of inertia.

2. Newton's Second Law

The rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction in which the force acts.

F = dp/dt = d(mv)/dt = ma Force = mass × acceleration (for constant mass).

3. Newton's Third Law

To every action, there is always an equal and opposite reaction. Action and reaction forces act on different bodies, so they do not cancel each other out.

4. Conservation of Linear Momentum

Law of Conservation

If no external force acts on a system of colliding objects, the total momentum of the system before collision is equal to the total momentum after collision.
m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

5. Friction

An opposing force that comes into play when one body moves or tends to move over the surface of another body.

Static Friction (fs): Self-adjusting force. Maximum value is Limiting Friction (fs_max = μs N).
Kinetic Friction (fk): Friction when body is actually moving (fk = μk N). μk is always less than μs.