A rock with a mass of 10 lb falls 100 ft from a cliff to the floor of a canyon. What is the change in potential energy (Δ PE ) of the rock?

Question

Accepted Answer

1 lb = 0.4536 kg; thus, 10 lb= 4.536 kg

1 in = 2.54 cm; thus, 1 m =100 cm and 1 ft = 12 in ; therefore, 100 ft = 30.48 m

ΔPE = mgΔh

[latex]ΔPE = (4.536 kg)(9.81 m/s^2)(-30.48 m)[/latex]

[latex]=-1356 kg . m^2 .s^{-2}[/latex]

[latex]1 N = 1 kg .m.s^{-1} and 1 J = 1 N.m[/latex]

[latex]ΔPE = -1356 J [/latex]

Question 1.12.2: A rock with a mass of 10 lb falls 100 ft from a cliff to the...