A device consists of eight balls, each of mass 0.8 kg attached to the ends of low-mass spokes of length 1.4 m, so the radius
of rotation of the balls is 0.7 m. The device is mounted in the vertical plane, as shown in Figure 11.87. The axle is held up
by supports that are not shown, and the wheel is free to rotate on the nearly frictionless axle. A lump of clay with mass 0.20
kg falls and sticks to one of the balls at the location shown, when the spoke attached to that ball is at 45 degrees to the
horizontal. Just before the impact the clay has a speed 9 m/s, and the wheel is rotating counterclockwise with angular speed
0.23 radians/s.
(C) There is no change because linear momentum is always conserved.
(D) The downward linear momentum decreases because the axle exerts an upward force.
(f) Qualitatively, what happens to the total kinetic energy of the combined system? Why?
(A) Some of the kinetic energy is changed into linear momentum.
(B) Some of the kinetic energy is changed into angular momentum.
(C) The total kinetic energy decreases because there is an increase of internal energy in this inelastic collision.
(D) There is no change because kinetic energy is always conserved.