Q1. When a surface is irradiated with light of wavelength 4950 A , a photo current appears that vanishes if a retarding potential greater than o.6V is applied across the photo tube. When different source of light is used, it is found that the critical retarding potential is changed to 1.1 V. Find the work function of the emitting surface and the wavelength of the second source.
Q2. A 330 piano slides 3.8 down a 34 incline and is kept from accelerating by a man who is pushing back on it parallel to the incline .The effective coefficient of kinetic friction is 0.32.
Determine the force exerted by the man
determine the work done by the man on the piano
determine the work done by the friction force.
Determine the work done by the force of gravity.
Determine the net work done on the piano.