Question

what is the best description of the acceleration of an object?
a runner travels 100 m in one minute.
a car’s velocity changes from 25 m/s to 20 m/s in 5 seconds.
a remote - control car speeds up from 0 m/s to 15 m/s.
an airplane changes elevation from 10,000 ft to 5,000 ft.

Explanation:

Acceleration is the rate of change of velocity. The first option gives speed (distance over time). The fourth option gives a change in elevation which is not related to acceleration in the context of linear - motion acceleration. The third option just states a speed - up without time. The second option gives an initial velocity, a final velocity, and a time interval, which can be used to calculate acceleration ($a=\frac{v_f - v_i}{t}$, where $v_f$ is final velocity, $v_i$ is initial velocity and $t$ is time).

Answer:

A car’s velocity changes from 25 m/s to 20 m/s in 5 seconds.