physics question

Question

A car with speed v and an identical car with speed 2v both travel the same circular section of an unbanked road. If the frictional force required to keep the faster car on the road without skidding is F, then the frictional force required to keep the slower car on the road without skidding is

a. 4F

b. 2F

c. F

d. F/2

e. F/4

Answer 1

Centripetal force is 1/r * m * v²

where r is the radius of the circle, m is the mass of the object, and v is the tangential velocity.

To keep from slipping, the faster car needs 4X the frictional force. So the correct answer is d)