
#1
Nov2607, 07:10 PM

P: 605

1. The problem statement, all variables and given/known data
A dentist's chair of mass 207kg is supported by a hydraulic lift having a large piston of crosssectional area 1403.0cm^2. The dentist has a foot pedal attached to a small piston of crosssectional area 78.0cm^2. What force must be applied to the small piston to raise the chair. 2. Relevant equations P=F/A Fp/Ap = Fc/Ac 3. The attempt at a solution Fp = Fc/Ac * Ap Fp = 207kg/1403 * 78 = 112.78 Okay so I have already gotten the answer 112.78N but I don't understand a few things about this question...  Why does Fp/Ap = Fc/Ac??  Why is 207kg relate to 1403cm^2?  What is the subscripts p and c??? 



#2
Nov2607, 07:50 PM

HW Helper
P: 6,214

Suggestion in your calculations when you said...
"Why does Fp/Ap = Fc/Ac??" Does this not mean that [itex]P_p=P_c[/itex] which just basically says that pressure is transmitted equally throughout a fluid...i.e. the pressure at one end is equal to the pressure at the other. the subscripts p and c would be piston and chair respectively 


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