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Solved: Down the Pole. A fireman of mass m slides a
Chapter 7, Problem 61P(choose chapter or problem)
Problem 61P
Down the Pole. A fireman of mass m slides a distance d down a pole. He starts from rest. He moves as fast at the bottom as if he had stepped off a platform a distance h ≤ d above the ground and descended with negligible air resistance. (a) What average friction force did the fireman exert on the pole? Does your answer make sense in the special case of h = d and h = 0? (b) Find a numerical value for the average fiction force 75 kg fireman exerts, for d = 2.5 m and h = 1.0 m. (c) In terms of g, h, and d. what is the speed of the fireman when he is a distance y above the bottom of the pole?
Questions & Answers
QUESTION:
Problem 61P
Down the Pole. A fireman of mass m slides a distance d down a pole. He starts from rest. He moves as fast at the bottom as if he had stepped off a platform a distance h ≤ d above the ground and descended with negligible air resistance. (a) What average friction force did the fireman exert on the pole? Does your answer make sense in the special case of h = d and h = 0? (b) Find a numerical value for the average fiction force 75 kg fireman exerts, for d = 2.5 m and h = 1.0 m. (c) In terms of g, h, and d. what is the speed of the fireman when he is a distance y above the bottom of the pole?
ANSWER:
Solution 61P
Step 1 of 3:
Motion from top to bottom of pole(y=0 at bottom)
We have and substitute in above equation
The equation for f gives f=mg in this case .When f=mg the forces on him cancel and doesn’t accelerate down the pole, which agrees with .