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.
