# Object being pushed up an inclined plane

1. ### Bushman

3
I can't figure out how to get the mass of this object, with the information given:

Inclined plane with angle relative to the ground of 20 degrees.

It takes 70 Newtons to get the object moving up the plane.

"Mu" of static friction: 0.35

All my example problems involve an object going down an inclined plane. I have been working on this problem all day, and just seem to get myself more and more confused. Any help would be appreciated.

2. ### andrewchang

221
try drawing a free body diagram- the forces acting on the block are the push, friction, the normal force, and weight.

3. ### Bushman

3
I have :(. I don't know the weight, only what I gave above. It seems to me like I need one more piece of information, such as the weight. That is why I posted here, to see if I was missing something obvious.

Last edited: Dec 14, 2005
4. ### andrewchang

221
well, you are solving for the weight, to get the mass.

you know that $F_f = \mu N = \mu Wcos(\Theta)$

5. ### Bushman

3
So that means:

Fsubf = 24.5

24.5 = mu x W x cosTheta

24.5/(mu x cosTheta) = W

Thank you so much, I did not recall that relationship between the Friction force and muN.

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