24. A 78 g steel ball is released from rest and falls vertically onto a rigid surface. The ball strikes the surface and is in contact with it for 0.5 ms. The ball rebounds elastically, and returns to its original height
during a round trip of 4 s. Assume that the surface does not deform during contact. What is the
maximum elastic energy stored by the ball? (Use acceleration due to gravity g = 10 m/s2)
A. 23.1)
B. 43)
C. 11.5 J
D. 15.6)

stands for electromotive force and it is measured in volts. despite its name, it is not actually the force in the sense of being a "pushing" or "pulling" (not measured in newtons).an equation that relates emf,  ℰ,  to a battery's terminal voltage, v, current, i, and internal resistance, r, is    ℰ = v + irin this case, the emf can be interpreted as a voltage—a difference in electric potential.i would not say that it would be considered an energy. if emf can be defined as the energy/work per a unit charge from a battery or other electric source, then it is not strictly energy.

At maximum height, kinetic energy is converted in potential energy  formula: at max height, ke = ½ * 0.27kg * (16m/s) ² = 34.56 j  so the remaining pe = (41.70 – 34.56)= 7.14 j = 0.27 kg * 9.8m/s² * h  = (9.8/7.14 * 0.27)so max height h = 5.08 or 5 m