Let's assume that ground level is the height 0 meters. The change in potential energy is going to be gravitational potential energy, which is given by PE=mgh.
ΔPE=mgh-mgy
=mg(h-y)
=50(28-0)
=1400 J
Friction is used to refer to forces that resist relative motion, in general,whereas viscosity refers specifically to resistive forces that occur between layers of a fluid when fluids attempt to flow. Fluid friction is the force that resists the movement of a solid object through a fluid(liquid or gas). Sky divers falling down through the sky experience a type of fluid frictioncalled air resistance.
Answer:
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