A race car going around a flat, unbanked circular track gradually increases spee
ID: 1487153 • Letter: A
Question
A race car going around a flat, unbanked circular track gradually increases speed as it
completes one full trip around the track. Which of the following can explain why the car gains
speed?
(A)
Energy stored in the fuel is converted to mechanical energy.
(B)
A component of the frictional force exerted by the ground on the tires is directed toward
the center of the circle.
(C)
A component of the frictional force exerted by the ground on the tires is in the direction of
motion.
(D)
The car’s velocity and acceleration are perpendicular.
The question are
1. which answer is obvious and what law of physics does this illustrate
2. The other correct answer has to do with how work can be either positive or netgative. If the car gain speed what is the sign of work? what does that mean about directions of other quantities?
Explanation / Answer
A and C are the correct answers.
1)For A the law of conservation of energy applies.
2)For C, the work is done against friction. It will be negative. If the car gains speed the the work done will remain negative.