Suppose that a NASCAR race car is moving to the right with a constant velocity of +82 m/s. What is the average acceleration of the car? (b) Twelve seconds later, the car is halfway around the track and traveling in the opposite direction with the same speed. What is the average acceleration of the car?

I understand (b), but not (a). How can I find acceleration when time is not given?

Question

Suppose that a NASCAR race car is moving to the right with a constant velocity of +82 m/s. What is the average acceleration of the car? (b) Twelve seconds later, the car is halfway around the track and traveling in the opposite direction with the same speed. What is the average acceleration of the car?

I understand (b), but not (a). How can I find acceleration when time is not given?

unklerhaukus · Answer

If the car has constant velocity it is not accelerating

$$a= {dv \over dt^{}} $$

anonymous · Answer

So it would be zero?

unklerhaukus · Answer

At constant velocity Acceleration is zero

anonymous · Answer

Not quite true, it's changing direction, so it still has acceleration. When moving in a circle, tangential acceleration is v^2/r.

anonymous · Answer

Also, as a side note, since the car appears to be undergoing uniform circular motion (hence the constant speed and tangential acceleration), the tangential acceleration will be of the same magnitude, just with a vector pointing in the opposite direction. That is, if I've understood the question correctly.

unklerhaukus · Answer

the car is moving to the right,