Asked by Neha

A box of books weighing 303 N moves with a constant velocity across the floor when it is pushed with a force of 400 N exerted down-ward at an angle of 38.6 degrees below the horizontal.
Find ìk between the box and the floor.

Well I know that I have to use netF = ma, so I gotta find the x and y components of the 400 (sin/cos38.6). A = 0 cuz constant velocity. So the RHS of Fx = max and Fy = may is always 0, then I have to add/subtract the y and x forces to get certain ones. Then I have to put the normal force and max kinetic force in the eq. maxkin = normal * ìk. But what I don't get is how can the books be in N? I mean, I don't think that's a unit of weight, but of a force. Should I get the right answer with the steps that I put up there? Thanks!
Answered by Neha
Sorry where it says ik it should be the microsign and then k
Answered by Neha
oh wait nvm it can be N b/c force of gravity = weight
Answered by Neha
i got 26.95...seems high
Answered by Neha
I know that coefficients generally don't exceed 1, so I have no idea what to do
Answered by Neha
i redid it and got 1.205 which is wrong. can someone please help me?
Answered by bobpursley
get the components of the pushing force.
Vertical,downward: 400sin38.6
Horizonal, pushin: 400cos38.6

Next,friction force: mu*Fn=mu(400+verticaldownwardforce)

Next, at constant velocity, then net force is zero, or

Netforce=horizonalforce-frictionforce=0

solve for mu.
Answered by Neha
that's what i did before, and it's still wrong
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