Mechanical Advantage-
The pulley system shown in the figure is used to lift a 52- crate. Note that one chain connects the upper pulley to the ceiling and a second chain connects the lower pulley to the crate. Assume the masses of the chains, pulleys, and ropes are negligible.

Q1: Determine the force required to lift the crate with constant speed.

Q2:Determine the tension in the upper chain.

Q3: Determine the tension in lower chain.


Okay so to find Force I did:
Fnet=F+F-mg
F=Mg/2

52(9.81)/2 =255.06 or 260( they want it in 2 sig figs)
When I checked answer it said this was not right?!

What am I doing wrong.

I know top and bottom tension should equal. I'm just having a hard time finding F.

Thanks for help

Um... there is no image :(

Here you go:
http://www.flickr.com/photos/49708296@N04/5051943688/


If that doesn't work. Here is link.
http://www.flickr.com/photos/49708296@N04/5051943688/

Quote:

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Originally Posted by heyyalliee

Okay so to find Force I did:
Fnet=F+F-mg
F=Mg/2

52(9.81)/2 =255.06 or 260( they want it in 2 sig figs)
When I checked answer it said this was not right?!

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Perhaps they used a value of g = 9.8 m/s^2? That would give an answer of 52(9.8)/2 = 254.8 N, which rounds down to 250 N.

Yes, giving 52 kg (which is 2 sf) suggests that you use g = 9.8 m/s^2 (which is 2 sf) and the answer in 2 sf too.

The next two parts should be easy :)