Suppose a highway curve is properly banked to eliminate friction for a speed of 45 mph. if your tires were bald and you wanted to avoid sliding on the road, you would have to drive:

a) at exactly 45 mph.
b) somewhat above 45 mph
c) somewhat below 45 mph.

a) at exactly 45 mph.

Explanation:

When road is banked at the given angle then the force equations for the car is given as

in vertical direction

In horizontal direction

so we have

now we have

so here we have all values are constant for a given speed

so the correct answer will be

a) at exactly 45 mph.

v=ir = 3x15 =45 v

b.a device that inputs heat into a cool object