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mybrohshi5
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Homework Statement
A block of mass 1.2 kg rests on top of another block of mass 1.8 kg, which rests on a frictionless surface. The coefficient of static friction between the blocks is mu_s = 0.3.
(a) What is the maximum horizontal force that can be applied to the upper block so that the blocks accelerate together, without the upper block sliding on the lower one?
(b) Suppose that the force is applied to the lower block instead; what is the maximum horizontal force that can be applied in this case so that the blocks will accelerate together, without any slipping between the two?
Homework Equations
f=ma
μs=fs/n
The Attempt at a Solution
Not sure how to start going about this one.
I tried this but it didnt work out to be right and i think i am leaving something out.
i found the normal force on the top block
n=1.2(9.8) = 11.76
then i found the fs
0.3 = fs/11.76
fs=3.528
i knew that wasnt right cause i didnt include anything about the bottom block moving with the top block so i found the fs of this bottom block as well
0.3 = fs/17.64
fs = 5.292
Not sure what to do now? i think if i add the two fs's together that will give me part (b) which would be 8.82 N for the force and i believe that is correct but I am not sure how to get part (a)
Any help would be appreciated.
Thank you :)