Circular freeway entrance and exit ramps are commonly banked to handle a car moving at 13 m/s. To design a similar ramp for 26 m/s one should:
A) increase radius by factor of 2
B) decrease radius by factor of 2
C) increase radius by factor of 4
D) decrease radius by factor of 4

Question

Circular freeway entrance and exit ramps are commonly banked to handle a car moving at 13 m/s. To design a similar ramp for 26 m/s one should:
A) increase radius by factor of 2 
B) decrease radius by factor of 2 
C) increase radius by factor of 4 
D) decrease radius by factor of 4

Quizplus · Accepted Answer

The centripetal force required to keep a car in circular motion is proportional to the square of the velocity and inversely proportional to the radius of curvature. Therefore, to design a ramp for double the velocity (i.e. 26 m/s), the radius of curvature should be increased by a factor of 4. Thus, choice C is the best answer.

Circular Freeway Entrance and Exit Ramps Are Commonly Banked to Handle