Question

A block is pushed on the ground with an initial velocity of 20 $\frac{m}{s}$, it stops after 6 seconds. What is the average retardation of the block?

• A. $\frac{-10}{3}\frac{m}{s^2}$
• B. $\frac{10}{6}\frac{m}{s^2}$
• C. $\frac{20}{3}\frac{m}{s^2}$
• D. $\frac{10}{3}\frac{m}{s^2}$

Answer 1

The correct option is D

$\frac{10}{3}\frac{m}{s^2}$

Given, initial velocity, $u=20\frac{m}{s}$ and time, $t=6s$

Since the block comes to a stop, the final velocity is zero $v=0$.

Average Acceleration $a=\frac{v-u}{t}$

$\Rightarrow a=\frac{0-20}{6}$

$\Rightarrow a=\frac{-10}{3}\frac{m}{s^2}$

The negative sign indicates the body is slowing down. So, the average retardation or deceleration of the body is = $\frac{10}{3}\frac{m}{s^2}$