Answer:
2849.98 J
Explanation:
From the question,
Work done by the boy = change Potential energy of the boy + change in kinetic energy of the boy
W = ΔP + ΔK..................... Equation 1
Where W = work done by the boy, ΔP = change in potential energy of the boy, ΔK = Change in kinetic energy of the boy.
But,
ΔP = mgΔh.................... Equation 2
ΔK = 1/2mΔv²................. Equation 3
Where m = mass of the boy, Δh = change in height of the boy, Δv = change in velocity of the boy.
Substitute equation 2 and 3 into equation 1
W = mgΔh+1/2mΔv²................. Equation 4
Given: m = 72 kg, Δh = 1.61 m, Δv = 8.5-1.6 = 6.9 m/s, g = 9.8 m/s²
Substitute into equation 4
W = 72(9.8)(1.61)+1/2(72)(6.9²)
W = 1136.016+1713.96
W = 2849.98 J
