Kinematics Question 492

Question: The driver of a car travelling at velocity v suddenly see a broad wall in front of him at a distance d. He should [IIT 1977]

Options:

A) Brake sharply

B) Turn sharply

C) (a) and (b) both

D) None of the above

Show Answer

Answer:

Correct Answer: A

Solution:

When driver applies brakes and the car covers distance x before coming to rest, under the effect of retarding force F then $ \frac{1}{2}mv^{2}=Fx $

therefore $ x=\frac{mv^{2}}{2F} $

But when he takes turn then $ \frac{mv^{2}}{r}=F $

therefore $ r=\frac{mv^{2}}{F} $

It’s clear that $ x=r/2 $ i.e. by the same retarding force the car can be stopped in a less distance if the driver apply breaks.

this retarding force is actually a friction force.



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