A 75-kg roofer climbs a vertical 7.0-m ladder to the flat roof of a house. He th

Question

A 75-kg roofer climbs a vertical 7.0-m ladder to the flat roof of a house. He then walks 12 m on the roof, climbs down another vertical 7.0-m ladder, and finally walks on the ground back to his starting point.

Part A

How much work is done on him by gravity as he climbs up?

Express your answer using two significant figures.

Part B

How much work is done on him by gravity as he climbs down?

Express your answer using two significant figures.

Part C

How much work is done on him by gravity as he walks on the roof?

Express your answer using two significant figures.

Part D

How much work is done on him by gravity as he walks on the ground?

Express your answer using two significant figures.

Part E

What is the total work done on him by gravity during this round trip?

Express your answer using two significant figures.

Part C

How much work is done on him by gravity as he walks on the roof?

Express your answer using two significant figures.

Part D

How much work is done on him by gravity as he walks on the ground?

Express your answer using two significant figures.

Part E

What is the total work done on him by gravity during this round trip?

Express your answer using two significant figures.

Explanation / Answer

a) W=mgh => W= -75 x 9.8 x 7 = -5100 J (negative work done as the climber is going in the opposite direction to the gravity)
b) W=mgh= same as above but the work will be positive = 5100 J
c) W=mgh => W=75 x 9.8 x 0=0
d) same as above (c) part = 0
e) total work done is zero because work done is the scalar product of force and Displacement( as he came back to his statring point so no work is done).Also gravitational forces are conservative forces.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.