A bicycle wheel is rotating anticlockwise at

PHYSICS · Multi-part · A Level · Physics · Engineering physics · Engineering physics

Problem

8\,\text{rad}\,\text{s}^{-1}

. The rider applies the brake so that the wheel comes to rest in

2\,\text{s}

and then starts rotating clockwise reaching

6\,\text{rad}\,\text{s}^{-1}

in the next

3\,\text{s}

. Take anticlockwise as the positive sense. (i) What is the sign of the angular acceleration during the first

2\,\text{s}

? Give a brief reason. (ii) What is the sign of the angular acceleration during the next

3\,\text{s}

? Give a brief reason.