- #1
SnakeDoc
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- 1
Homework Statement
A 2.60 kg block is initially at rest on a horizontal surface. A horizontal force F→ of magnitude 7.39 N and a vertical force P→ are then applied to the block (see the figure). The coefficients of friction for the block and surface are μs = 0.4 and μk = 0.25. Determine the magnitude of the frictional force acting on the block if the magnitude of P→ is(a)6.00 N and (b)9.00 N. (The upward pull is insufficient to move the block vertically.)
Homework Equations
f=μN
F=MA
N=mg-P
The Attempt at a Solution
So first I wrote the x and y forces separately
Fx=max
max=F→-ƒk
Fy=may
may=-mg+N+P the y acceleration is equal to zero
0=-mg+N+P
N=mg-P
Then I found the maximum possible values of μs for both values of P
μ*N=.4*(2.6*9.81-6)=7.8024
μ*N=.4*(2.6*9.81-9)=6.6024
I was able to get b as 4.31 by Fk=μk*N
but I'm not sure what to do for part a because the maximum value for P=6N is higher than the F→ force and I tried doing the same as part b but it says the answer is wrong.