A 10-foot-long chain weighs 25 lbs. And hangs from a ceiling. Calculate the work done in raising the lower end of the chain to the ceiling so that it is at the same level as the upper end.

varice2r

varice2r

Answered question

2022-09-05

A 10-foot-long chain weighs 25 lbs. And hangs from a ceiling. Calculate the work done in raising the lower end of the chain to the ceiling so that it is at the same level as the upper end.

Answer & Explanation

Willie Gilmore

Willie Gilmore

Beginner2022-09-06Added 8 answers

Step 1
It may help to visualize this as a differential equation. That is, the change in the amount of work done is dependent on the height of the lower end of the chain. So for every foot the chain is raised (y) the work increases by 2.5 2 . So we can write this as:
d W d y = 2.5 y 2
Separating the variables gives us:
d W = 2.5 y 2 d y
Then integrating both sides gives the equation from eng2math in answer 1.
Phoenix Burch

Phoenix Burch

Beginner2022-09-07Added 11 answers

Step 1
You can express the weight of the portion you are lifting as a function of the distance it is being raised by, call it y. So the work done is
W = a b F ( y ) d y
Remark that when you lift the tail of the chain up to the head, you end up with a 'u' shape, so we are lifting a length of y 2 feet. So, the chain is 25 10 = 2.5 pounds per foot so,
W = 0 10 2.5 ( y 2 ) d y = 2.5 y 2 4 | 0 10 = 62.5
This might be more appropriate for physics stack exchange, because the trickiness is more physical insight rather than integration.

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