In which situations is work being done? Hannah leans against her locker, but it doesn’t move.

Andy’s car rolls down a hill with the engine off.

A wind turbine stands still on a sunny, windless day.

A balloon expands as it is heated by the sun.

James pedals a stationary exercise cycle that doesn’t move.

Review multiple-concept example 7 in this chapter as an aid in solving this problem. in a fast-pitch softball game the pitcher is impressive to watch, as she delivers a pitch by rapidly whirling her arm around so that the ball in her hand moves in a circle. in one instance, the radius of the circle is 0.626 m. at one point on this circle, the ball has an angular acceleration of 66.1 rad/s2 and an angular speed of 12.6 rad/s. (a) find the magnitude of the total acceleration (centripetal plus tangential) of the ball. (b) determine the angle of the total acceleration relative to the radial direction.