# Experimentally Determine Coefficient of Static Friction

I need to determine the coefficient of static friction for the following set-up.

M1 = 380.45g
M2 = 74.7g

This is what I know... u=F/mg

What I can't figure out is how to factor in the horizontal and vertical weights.

Can anyone help?

Thanks!

#### Attachments

• static friction.bmp
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I should clarify.. those weights are the weights where the system just begins to move.

Doc Al
Mentor
Hint: What does the tension in the string equal?

OK, the tension for both is the same.. and it is equal to.... M2g I think ?

I'll keep thinking on this..

Thanks

Doc Al
Mentor
Right. There's a single tension in the string and it equals $M_2g$.

So, what must the friction force equal?

OK, here's what I think... the force must equal the tension (M2g), which is equal to uN.

What is N then? The mass of M1??

Doc Al
Mentor
OK, here's what I think... the force must equal the tension (M2g), which is equal to uN.
Good!

What is N then? The mass of M1??
Not the mass but the weight of M1.

Yes, the weight!

Thanks a bunch for your help!