Arturo O. answered 02/17/20
Experienced Physics Teacher for Physics Tutoring
The work done by friction should equal the difference between the actual kinetic energy at the bottom, and the expected kinetic energy based on the initial height.
Actual kinetic energy:
K = mv2/2
Expected kinetic energy:
K0 = mgh = mgLsinθ
Work done by friction (should come out negative):
W = K - K0 = mv2/2 - mgLsinθ = m(v2/2 - gLsinθ)
Plug in the values of m, v, g, L, and θ, in correct units. By the way, you did not provide the units for most of these quantities.