Question

A constant retarding force of $80\,N$ is applied to a body of mass $50\,kg$ which is moving initially with a speed of $20\,m/s$ . What would be the time required by the body to come to rest?

• A. $15\,\,s$
• B. $14\,\,s$
• C. $12.5\,\,s$
• D. $18\,\,s$

Answer 1

Answer: (C)

$12.5\,\,s$

Answer 2

Here, $a=\frac{F}{m}=\frac{80}{50}=1.6\,m/{{s}^{2}}$
$u=20\,m/s$ and $v=0$
From $v=u+at$
$0=20-1.6\times t$
$t=\frac{20}{16}=12.5\,s$