A student sits on a rotating stool holding two 5 kg objects. When his arms are extended
horizontally, the objects are 1.1 m from the
axis of rotation, and he rotates with angular
speed of 0.73 rad/sec. The moment of inertia of the student plus the stool is 2 kg m2
and is assumed to be constant. The student
then pulls the objects horizontally to a radius
0.31 m from the rotation axis.

Car batteries are often rated in amp-hours. this rating indicates the quantity of charge that can pass through the battery before the battery's chemical energy must be restored by the car's generator or some other source. the amp-hour unit is convenient for simple calculations. for example, a 60-amp-hour battery can supply a current of 1.0 a for 60 h (or 60 a for 1.0 h) before going dead. find the energy stored in the following. (a) a 58 a-h, 10 v car battery(b) a 1.3 a-h, 1.7 v flashlight battery