- A 72-kg boy is surfing and catches a wave which gives him an initial speed of
ID: 1422130 • Letter: #
Question
- A 72-kg boy is surfing and catches a wave which gives him an initial speed of 1.6 m/s. He then drops through a height of 1.57 m, and ends with a speed of 8.5 m/s. How much nonconservative work was done on the boy?
- Shoveling snow can be extremely taxing since the arms have such a low efficiency in this activity. Suppose a person shoveling a sidewalk metabolizes food at the rate of 850 W. (The efficiency of a person shoveling is 3%.) (a) What is her useful power output? (b) How long will it take her to lift 2700 kg of snow 1.20 m? (This could be the amount of heavy snow on 60.0 ft of sidewalk.) (c) How much waste heat will she generate in the process?
Explanation / Answer
W = E2- E1
W = 0.5*mv^2 - (0.5*mu^2 + mgh)
W = 1,36 kJ
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