Speed and Velocity are both measures of distance travelled in a given time and are therefore calculated using Speed=Distance/Time.Speed is a scalar quantity which means that it is quantified by a magnitude only. Velocity is a vector quantity whcih means that it is quantified by a magnitude and a direction (it can also be considered to be speed in a given direction).Acceleration is the rate of change of velocity, which means that it is the measure of change in velocity over a given time. Since it is a change in velocity rather than a change in speed, the change described could be a change in magnitude, a change in direction, or a change in both of these values. Acceleration is also a vector quantity.