Momentum and Newton's Laws

Ever wondered why a moving lorry is harder to stop than a moving bicycle? That's momentum in action - the property that combines an object's mass and velocity into one powerful concept.

Momentum is calculated using the simple formula: momentum = mass × velocity $P = mv$. It's measured in kg⋅m/s, and here's the brilliant bit: in a closed system, momentum is always conserved - meaning the total momentum before an event equals the total momentum after.

Newton's First Law tells us that objects are naturally lazy - they'll stay at rest or keep moving at constant velocity unless an external force pushes them around. This laziness is called inertia, which measures how difficult it is to change an object's velocity.

When forces aren't balanced, Newton's Second Law kicks in $F = ma$, changing an object's speed, direction, or even shape. Remember Newton's Third Law: for every action, there's an equal and opposite reaction - like when you walk forward by pushing backwards against the ground.

Key Insight: Changes in momentum occur when F = (Δmv)/Δt, linking force directly to how quickly momentum changes over time.