Velocity, speed and acceleration
Velocity
Velocity, speedThe distance travelled in a fixed time period, usually one second. and acceleration are words that we often use to describe motion. We talk about high-speed trains, the acceleration of a sprinter or a Formula 1 racing car. In Physics these words have a precise meaning.
We use words like speed, constant speedWhen the speed of body does not change, eg the car was travelling at a constant speed of 30 m s-1., average speed and uniform acceleration to describe different types of motion.
The speed of an object does not require a direction to be considered, it simply has a value and unit, for example, 27 \(m\,s^{-1}\).
Velocity is a vector quantity which requires a value, unit and direction, for example, 49 \(m\,s^{-1}\) to the left.
Speed-time graphs can be used to represent motions involving speed and uniform acceleration.
Velocity-time graphs can be used to represent the motion of objects travelling in a straight line, for example backward and forward, up and down, a positive and negative direction.