GCSE SCIENCE PHYSICS HIGH SCHOOL - Forces and Motion - Distance - Displacement - Speed - Velocity

Distance, Displacement, Speed and Velocity.

Distance is a measure of how far an object has travelled from its starting point,
or how far away it is.
Distance is the same as length and is measured in metres.

Displacement is also a measure of how far an object has travelled from its
starting point but displacement also tells you the direction of the object.
Distance is a scalar and displacement is a vector.

Speed is a measure of how fast an object is moving.
It is measured in metres per second, written as m/s.

Speed = Distance ÷ Time.

Velocity is similar to speed.
It is also a measure of how fast an object is moving and is measured in m/s.

Velocity = Distance ÷ Time.

If an object is stationary (not moving), then its speed or velocity is zero.

The difference between velocity and speed is that
velocity is speed in a certain direction (see scalars and vectors).
If an object is moving in a straight line,
then its speed and velocity will be the same.
If the moving object stays at the same speed but changes direction,
then we say that the velocity has changed (because the direction has changed)
but the speed has stayed the same.

If the velocity in one direction is positive (for example, forwards at 10m/s)
then the velocity in the opposite direction is negative (for example, backwards at -10m/s).

In most of the examples of motion that you will come across,
the object will be moving in a straight line.
In this case, use the word velocity rather than speed
(see the next page for calculations).

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