Question

What is acceleration?

The change in motion of an object.

The change in speed and/or direction of an object.

The change in speed of an object.

The speed of an object.

Answer 1

Acceleration is the rate of change of velocity or speed, or a physical quantity that defines how quickly speed or velocity changes:

$$a=\frac{\Delta v}{\Delta t}=\frac{v_2-v_1}{t_2-t_1}.$$

For instance, an RC car increased the speed from 0 (rest) to 20 m/s in just 20 seconds, then the acceleration will be

$$a=\frac{20-0}{20}=1\text{ m/s}^2.$$

As we see, acceleration is measured in meters per second squared.