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offbeatjumi
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Homework Statement
An object of mass 0.2 kg with initial velocity 4.8 m/s slides a horizontal distance of 3.0 m before coming to rest (final velocity is 0 m/s). What is the coefficient of kinetic friction on the surface?
Homework Equations
K + U - W(other) = 0 ...conservation of energy
The Attempt at a Solution
I have delta-K = 0 - (1/2)(0.2)(4.8)^2 = -0.48 J
delta-U is zero since there is no change in y
W(other) would be just the work done by the frictional force f(k).
f(k) <= (mu)kn...where n-mg = 0... so n = mg = 1.96 N ...f(k) <= (mu)k*1.96N
W = F*d... F = f(s)...
since U = 0 ... K - W(other) = 0... K = W(other) = -0.48 J
F*d = -0.48 J
(mu)k*1.96N*3.0m = -0.48 J
Solving for (mu)k I get (mu)k = 0.0816.
From the back of the book I know this is wrong, the given answer is 0.392.
What am I doing wrong?
Thanks!