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Need help by tonight(again)!

  • #1
I'm stuck on two problems 1 is #8(please see the pdf file):
I know I have to solve this equation with this:
F=MA
I calcualated F by taking the magnitude of Fx and Fy:
Fx=390*cos(9)i+335*cos(-28)
Fy=390*sin(9)i+335*sin(-28)

I got F as 687.756
and the mass is given: 3819kg

So I divided those and I got the answer as .180 but the comp. says it's wrong.

The second problem is 12(please see the pdf file):
I know I have to do this:
F = m*g-m*a*cos(angle)
(is it right?)

(I calculated the acceleration and it is right)
so F = 3.35*9.8-3.35*5.67*cos(27)
and I got 26.06. What's wrong? with this?

Thanks in advance for the help.
 

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  • #2
enigma
Staff Emeritus
Science Advisor
Gold Member
1,747
10
The first looks fine to me. Check your sig figs.

The second, I'm not exactly sure what it's asking for. It looks to me like it's asking what the normal force is (equal & opposite from what the block applies to the incline). I'm not sure though.
 

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