Adisk rotates freely on a vertical axis with an angular velocity of 30 rpm. an identical disk rotates above it in the same direction about the same axis, but without touching the lower disk, at 20 rpm. the upper disk then drops onto the lower disk. after a short time, because of friction, they rotate together. the final angular velocity of the disks is
a. 50 rpm
b. 40 rpm
c. 25 rpm
d. 20 rpm
e. 10 rpm

Red light strikes a metal surface and electrons are ejected. if violet light is now used with a 10% greater intensity, what will happen to the ejection rate (number of ejected electrons per second) and the maximum energy of the electrons? a) greater ejection rate; same maximum energyb) same ejection rate; greater maximum energyc) greater ejection rate; greater maximum energyd) same ejection rate; same maximum energye) none of the above answers are correct