Answer:
-42.68 J
Explanation:
Work done = weight x displacement
weight = 7 pound
= (7 x 4.45) N
= 31.15 N
Displacement = 54 inches
1 inch = 0.0254 m
54 in = 1.37 m
Work done = 31.15 N x 1.37 m x cos 180°
= -42.68 J
Thus, the amount of energy used to lift 7 pound object to 54 inches, 42.68 J of energy is used.