Dynamics

How forces combine, what balanced forces mean for motion, and how to draw force diagrams.

Friction is a force that opposes relative motion between surfaces in contact. Learn about static and kinetic friction.

Gravity is an attractive force between all objects with mass. Near Earth's surface, gravity pulls objects downward with a gravitational field strength of approximately 10 N/kg. Weight is the gravitational force on an object and is calculated using W = mg. Weight and mass are different quantities.

Momentum is a measure of how difficult it is to stop a moving object. It depends on both mass and velocity. Momentum is always conserved in a closed system — the total momentum before a collision equals the total momentum after.

Newton's three laws form the foundation of classical mechanics, describing how objects move under the influence of forces.

A moment is the turning effect of a force about a pivot. It is calculated by multiplying the force by the perpendicular distance from the pivot. For an object to be balanced (in equilibrium), the total clockwise moments must equal the total anticlockwise moments.

The difference between mass and weight, and how to calculate gravitational force.