It is not only moving objects whose speed can vary. The speed of the wind and the speed of sound also vary. A typical value for the speed of sound in air is about 330 m/s.

Acceleration close accelerationThe rate of change in speed (or velocity) is measured in metres per second squared. Acceleration = change of velocity ÷ time taken. is the rate of change of velocity.

Motion in a plane. Cases of uniform velocity and uniform acceleration-projectile motion. Uniform circular motion. Intuitive concept of force. Inertia. Newton's first law of motion; momentum and ...