Force necessary to support mass on Hydraulic Jack?

Force necessary to support mass on Hydraulic Jack???

Homework Statement

Piston 1 in the figure has a diameter of 1.31 cm. distance of 2 in
Piston 2 has a diameter of 7.91 cm. distance of 10 in
In the absence of friction, determine the force F, necessary to support an object with a mass of 904 kg placed on piston 2. (Neglect the height difference between the bottom of the two pistons, and assume that the pistons are massless).

Homework Equations

F1*d1 = Fp*d2, where d1 is the moment arm of F1, and d2 is
the moment arm of Fp.

The Attempt at a Solution

Fp = (F1*d1)/d2
(904)(9.81)/(pi)(0.003955)^2= F/(pi)(0.00655)^2
F=242.98 N which was incorrect.
anyone have an idea of what I should do and what equation to use? Thanks!

Answers and Replies

Redbelly98
Staff Emeritus
Science Advisor
Homework Helper

I think we'll need to see the figure before we can help you out.

http://img6.imageshack.us/img6/7849/1808317ca439856447261f7.gif [Broken]

this is the link for the picture.

Last edited by a moderator:
djeitnstine
Gold Member

Neglecting the height difference means the pressure should be the same, thus $$F_1 A_1 = F_2 A_2$$

This is would be the force exerted on the small piston.

You should know how to find the force needed by the hand from this.

Redbelly98
Staff Emeritus
Science Advisor
Homework Helper

Homework Equations

F1*d1 = Fp*d2, where d1 is the moment arm of F1, and d2 is
the moment arm of Fp.

The Attempt at a Solution

Fp = (F1*d1)/d2
(904)(9.81)/(pi)(0.003955)^2= F/(pi)(0.00655)^2
F=242.98 N which was incorrect.
anyone have an idea of what I should do and what equation to use? Thanks!

You have correctly found F1, the force on the smaller piston. However, they are asking for Fp (labelled simply F in the figure), the force exerted by the hand.

You have the equation to find Fp given F1.

ok. I used the equation given and solved for Fp. I had (242.98)(pi*(0.03955)^2))/(pi)*(0.00655)^2=Fp=8858.92 N, which is also incorrect.
what am I doing wrong?

nvm. I solved it! thanks everyone for your input!

nvm. I solved it! thanks everyone for your input!

how u solved it my friend?