3. A sphere, mass m, falls to the floor from a height h. The sphere rebounds to its original heighth following a perfectly elastic collision with the floor. During the time the sphere
is in contact with the floor, what is the average force the floor applies to the sphere?

Adielectric-filled parallel-plate capacitor has plate area a = 30.0 cm2 , plate separation d = 9.00 mm and dielectric constant k = 3.00. the capacitor is connected to a battery that creates a constant voltage v = 15.0 v . throughout the problem, use ϵ0 = 8.85x10-12 c2/n.m2 . find the energy u1 of the dielectric-filled capacitor.