Question

A body at rest is given an initial uniform acceleration of 8.0m/s for 30s after which the acceleration is reduced to 5.0m/s for the next 20s. Find the average retardation as the body is being brought to rest

Answer 1

I assume, retardation means the rate of acceleration change. Thus, the average retardation will be:

$$<r> = \dfrac{a_2 - a_1}{t}$$

where $a_1 = 8m/s^2$, $a_2 = 5m/s^2$ are the initial and final accelerations respectively, and $t=30s$ is the time period. Thus, have:

$$<r> = \dfrac{5m/s^2 - 8m/s^2}{30s} = -0.1m/s^3$$

ANswer. -0.1 m/s^3.