# Need help with algebra based physics problem

• May 6th 2010, 05:41 AM
ckylek
Need help with algebra based physics problem
A cook holds a 2.00 kg carton of milk at arm's length. What force http://www.webassign.net/images/boldF.gifB must be exerted by the biceps muscle? (Ignore the weight of the forearm.)
1 Nhttp://www.webassign.net/sercp/p8-9.gif

I have been trying for a while to figure this one out and its just not coming to me. I know the answer is supposed to be 312N. Any help would be appreciated. Thanks.
• May 6th 2010, 08:16 AM
HallsofIvy
First, this has nothing to do with "Linear and Abstract Algebra" and does not belong in this category.

Second, draw horizontal and vertical lines making a right triangle with $\displaystyle \vec{F}_B$ as hypotenuse. The vertical side is a "near side" to that 75 degree angle and will have magnitude $\displaystyle F_B cos(75)$. In order to support the milk carton, we must have $\displaystyle F_B cos(75)= 2.00$. Solve that for $\displaystyle F_B$.

That will give the force in "kg" which is really a mass. To get the force in Newtons, multiply by g= 9.81[/tex].
• May 6th 2010, 08:21 AM
TKHunny
1) Why is this in Abstract Algebra. It's a physics problem. Trigonometry at worst on this one.

2) Have you identified that you are dealing with a Type 3 Lever? That would be a good place to start.

3) What forces must be equal? 2 kg * (25 cm + 8 cm) should be related to (sine or cosine of 75º) * (bicep force) * (8 cm)

I'll leave the details to you. Let's see what you get.