A 75-{\ m kg} roofer climbs a vertical 7.0-{\ m m} ladder to the flat roof of a

Question

A 75-{ m kg} roofer climbs a vertical 7.0-{ m m} ladder to the flat roof of a house. He then walks 12 { m m} on the roof, climbs down another vertical 7.0-{ m m} ladder, and finally walks on the ground back to his starting point. A) How much work is done on him by gravity as he climbs up? B) How much work is done on him by gravity as he climbs down? C) How much work is done on him by gravity as he walks on the roof? D) How much work is done on him by gravity as he walks on the ground? E) What is the total work done on him by gravity during this round trip?

Explanation / Answer

a)Work done by gravity=-mgh=-5145J

b)Work done=mgh=5145J

c)Work done=0 (gravitational force is perpendicular to displacement)

d)Work done=0 (gravitational force is perpendicular to displacement)

e)Total work=0. (Since all forces are conservative and starting and end points are same.Adding work done also gives same result)

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