- #1
PEZenfuego
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Homework Statement
A 75 kg box slides down a 25 degree ramp with an acceleration of 3.60 m/s/s
Find the coefficient of kinetic friction (I'll use "uk") between the box and the ramp.
Find the acceleration for a 175 kg box.
Homework Equations
F=ma
Fg= mXg (g=9.81 m/s/s in my class)
uk= Fk/Fn
Solution: 0.061 and 3.61 m/s/s
This is kind of a curveball question compared to what we've had. The big difference is that the sum of the forces in the y direction does not equal 0...I am also pretty sure Fapp is 0 since there is no applied force.
The Attempt at a Solution
I wish I could include a drawing because that could be where the problem is...here was my go:
Fnet=Fk+Fp
Fnet=m X a
m X a=Fk-Fp
(Fk=(m X a)+(Fp)
Fp=cos(theta)m X g
Fn=sin(theta)m X g
uk=Fk/Fn
uk=((m X a)+(cos(theta)m X g))/(sin(theta) X m X g)
uk=((75X3.6)-(cos(25)X75X9.81))/sin(25)X75X9.81
uk=3.01 which is obviously way off...
I haven't tried to find the answer to the second part yet.
Any help would be very much appreciated.