A movie stuntman (mass 80 0 kg) stands on a window ledge 5 0m above the floor as

Question

A movie stuntman (mass 80 0 kg) stands on a window ledge 5 0m above the floor as in (Figure 1) Grabbrsg a ropo at attached to a chandelier he swings down to grapple with the movie's villain (mass 70 0 leg), who is standing directly under the chandeler (Assume that the stuntman's conic- of mass moves downward 4 0 m He releases the rope just as he reaches the villain) With what speed do the entwined foes start to slide across the floor? Express you answer in meters per second to two significant figures. If the coefficient of kinetic friction of their bodies with the floor is mu _K = 0 300. how far do they slide? Express your answer in meter to two significant figures.

Explanation / Answer

M . g . h = 0.5 . M . V^2

V^2 = 2 . 9.8 .4

V = 8.85 m/s

a) Conservation of momentum

MV = (M + m ) v

80 . 8.85 = ( 80 + 70) v

v = 4.72 m/s

b) Retarding force = µ . N = 0.3 . 150 . 9.8 = 441 N

Deceleration = Force / Mass = 441 / 150 = 2.94 m/s/s

Distance slid = V^2 / 2 . a =4.72^2 / 2 . 2.94 = 3.75 m

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