Question

The velocity of a retarding body changes from ${90ms}^{-1}$ to $36m{s}^{-1}$ in $9$ seconds. Find the retardation of a body?

• A. ${20ms}^{-2}$
• B. ${6ms}^{-2}$
• C. ${18ms}^{-2}$
• D. ${36ms}^{-2}$

Answer 1

Answer: (B)

${6ms}^{-2}$

Initial velocity $u=90m{s}^{-1}$

Final velocity $v=36m{s}^{-1}$

Time, $t=9s$

Using first equation of motion:

$v=u+at$

$\Rightarrow 36=90+a\times 9$

$\Rightarrow a=-6m/s^2$

Thus retardation is $6m/s^2$