Agust of wind blowing east pushes against a ball. when will the wind do work on the ball?

a) when the ball moves to the east
b) when the ball moves to the north
c) when the ball stays in one place
d) when the ball moves north or south

The uniform slender bar rests on a smooth horizon- tal surface when a force f is applied normal to the bar at point a. point a is observed to have an initial acceleration aa of 20 m/s2, and the bar has a corre- sponding angular acceleration of 18 rad /s2. deter- mine the distance b.