Physics Two Dimensional Motion Question 39
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 is 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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