A car travels east for 160 miles in 16 hours- what is the velocity. Velocity is the rate of change of displacement. Acceleration is change in velocity per change in time.
The velocity is a vector quantity and the speed is a scalar quantity.
An object can increase in speed or decrease in speed. Acceleration implies any change in the velocity of the object with respect to time. The velocity is a vector quantity and the speed is a scalar quantity. A roller coasters accelerates from an initial velocity of 60 ms to a final velocity of 70 ms over 4 seconds.