Phys101 Written Assignment #9 Solution
13.20. A hydraulic press for compacting powdered samples has a large cylinder which
is 10.0 cm in diameter, and a small cylinder with a diameter of 2.0 cm. A lever is
attached to the small cylinder as shown. The sample, which is placed on the large
cylinder, has an area of 4.0 cm2. What is the pressure on the sample if 350 N is applied
to the lever?
FN
C
The magnitude of force acting on the small cylinder is equal to FN.
In static equilibrium, all the torques about C should add up to zero:
FN l  350 (2l )  0
FN  350(2)  700 ( N )
The pressure applied to the fluid (through the small cylinder):
P
700
 2.0 10
2

 
2



2
 2.23 106 ( Pa )
The force of fluid on the large cylinder:
F  P R 2  2.23 106  0.05  1.75 10 4 ( N )
2
The pressure on the sample:
PS 
F 1.75 10 4 N

 4.4 107 ( N / m 2 )
4
2
A 4.0 10 m