MHT CET · Physics · Laws of Motion
The driver of a car travelling at velocity \(v\) suddenly see a broad wall in front of him at a distance \(d\). He should
- A brake sharply
- B turn sharply
- C Both (a) and (b)
- D None of these
Answer & Solution
Correct Answer
(A) brake sharply
Step-by-step Solution
Detailed explanation
When driver applies brakes and the car covers distance \(x\) before coming to rest, under the effect of retarding force \(F\).
Then
\(\begin{aligned}\frac{1}{2} m v^{2} &=F x \\x &=\frac{m v^{2}}{2 F}\end{aligned}\)
or
But when he takes turn, then
\(\begin{aligned}\frac{m v^{2}}{r} &=F \\r &=\frac{m v^{2}}{F}\end{aligned}\)
It is clear that \(x=\frac{r}{2}\)
ie, by the same retarding force the car can be stopped in a less distance if the driver apply brakes. This retarding force is actually a friction force.
Then
\(\begin{aligned}\frac{1}{2} m v^{2} &=F x \\x &=\frac{m v^{2}}{2 F}\end{aligned}\)
or
But when he takes turn, then
\(\begin{aligned}\frac{m v^{2}}{r} &=F \\r &=\frac{m v^{2}}{F}\end{aligned}\)
It is clear that \(x=\frac{r}{2}\)
ie, by the same retarding force the car can be stopped in a less distance if the driver apply brakes. This retarding force is actually a friction force.
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