A machine is rolling metal cylinder under pressure. The radius of the cylinder is decreasing at a constant rate of 0.05 inches per second and the volume V is 128 cubic inches. At what rate is the length H changing when the radius r is 2.5 inches?

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- Aug 22nd 2007, 08:46 AMSamantharate of change
A machine is rolling metal cylinder under pressure. The radius of the cylinder is decreasing at a constant rate of 0.05 inches per second and the volume V is 128 cubic inches. At what rate is the length H changing when the radius r is 2.5 inches?

- Aug 22nd 2007, 09:32 AMTKHunny
Use your hint.

Note: It would help if you could post in a less general category and profide a more descriptive title. It might give a clue as to your level or what class you are in or what tools should be used.

In this case, it's a nice differential calculus problem. If you're in a different class, that will be a problem.

r and h are functions of time.

V is constant, so dV = 0

dr is given as -0.05"/sec

Find dh when r = 2.5"

Complete derivative:

dV is known.

r is given.

dh/dt is what we need. We'll have to solve for it after everything else is found.

h - You will have to solve for this from the Hint.

dr/dt is given.

Substitute and solve.

Additional Note: Please show your work. It is a great place to learn where you are in your mathematics understanding. - Aug 22nd 2007, 09:42 AMSamantha
It's calc...I'mnot sure what to do =(

- Aug 22nd 2007, 01:08 PMTKHunny
Samantha, Samantha...I did nearly the entire problem for you. It is time for you to start showing a little more gumption. Please go read the previous post and pick out the statements that contain instructions for you to follow.

Really, there remains only a little algebra. If you cannot do it, you should go have a really frank conversation with your academic advisor.