1. A crate slides down a ramp that makes a 20angle with the ground. To keep the

Question

1. A crate slides down a ramp that makes a 20angle with the ground. To keep the crate from sliding too fast, Paige pushes back on it with a 62 N horizontal force.

question: How much work does Paige do on the crate as it slides 3.4 m down the ramp?

2. An escalator carries you from one level to the next in an airport terminal. The upper level is 4.7 mabove the lower level, and the length of the escalator is 7.7 m . Assume that your mass is64 kg .

question A : How much work does the up escalator do on you when you ride it from the lower level to the upper level?

question B:How much work does the down escalator do on you when you ride it from the upper level to the lower level?

Explanation / Answer

1. work done = F . d   (dot product )

        = |F| |d| cos@

|F| = 62 N and d = 3.4 m and @ = 180 - 20 = 160 deg

       = 62 x 3.4 x cos120 = - 198.1 J

2. A)

W = |F||d|cos@

F = mg = 64 x 9.8 = 627.2 N

d = 4.7 m

@ = 0

W = 627.2 x 4.7 = 2947.84 J

(B)

F = mg = 64 x 9.8 = 627.2 N

d = 4.7 m

@ = 180

W = 627.2 x 4.7 x cos180 = - 2947.84 J

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