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Verifying Hydraulics Question

by bcjochim07
Tags: hydraulics, verifying
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bcjochim07
#1
May9-08, 05:32 PM
P: 374
1. The problem statement, all variables and given/known data
A 55kg cheerleader uses an oil-filled hydraulic lift to hold four 110 kg football players at a height of 1 m. If her piston is 16 cm in diameter, what is the diameter of the football players' piston?


2. Relevant equations



3. The attempt at a solution

(55kg)(9.80)/(.02 m^2) = (440kg)(9.80)/A2
A2 = .16 m^2
.16 m^2 = pi * r^2
r=.2257 m
D= .45 m = 45 cm

Is this correct? I am a little bit confused as to the difference between these formulas:

p0 + F1/A1 = p0 + F2/A2 + ro*gh This is the one I used because she is just holding them in position and no work is being done.

for the formula DeltaF = ro*g (A1+A2)d2 You should use this one when the problem involves lifting something (doing work)
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bcjochim07
#2
May10-08, 08:12 PM
P: 374
any thoughts?


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