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# Does anyone know how to do this physics?

Initially, a ball has an angular velocity of 5.0 rad/s counterclockwise. Sometime later, after rotating through a total angle of 5.5 radians, the ball has an angular velocity of 1.5 rad/s clockwise.

a. What is the angular acceleration?

b. What is the average angular velocity?

c. How much time did this take?

Thanks, will award best answer!

### 2 Answers

- az_lenderLv 72 months agoFavorite Answer
b. If the angular acceleration was constant, the average angular velocity was 1.75 rad/s CCW.

a. 2*alpha*theta = (omega-f)^2 - (omega-0)^2 =>

alpha = [(1.5 rad/s)^2 - (5.0 rad/s)^2]/(2*5.5 rad) = -2.07 rad/s^2.

c. The time is (-6.5 rad/s)/(-2.07 rad/s^2) = around 3 seconds but use a calculator.

- Andrew SmithLv 72 months ago
The question is ambiguous. Does the "total angle" include the sum of counter clockwise + clockwise turns. Or does it mean the net result is 5.5 radians counterclockwise. az_lender has assumed a NET angle.

The two interpretations are so different as to need a different approach.