question_answer

A car weighing 1000 kg and traveling at 30 m/s stops at a distance of 50 m, retarding uniformly. What is the force exerted on it by the brakes? What is the work done by the brakes?

Answer:

               

\[m=1000\,kg\]	\[u=30\,m/s\]
\[V=0\]	\[S=50\,m\]
\[F=?\]	\[w=?\]

\[F=ma=m\left( \frac{{{v}^{2}}-{{u}^{2}}}{2s} \right)\] \[=\frac{-mu}{2s}=\frac{-1000\times 30\times 30}{2\times 50}\] \[=-900\times 1\] (or) Retarding force = 900 N \[W=F\times S\] \[=9000\times 50=4.5\times {{10}^{5}}J\]