A 39.0 kg box initially at rest is pushed 4.50 m along a rough, horizontal floor with a constant applied horizontal force of 135 N. If the coefficient of friction between box and floor is 0.300, find the following.

Question

A 39.0 kg box initially at rest is pushed 4.50 m along a rough, horizontal floor with a constant applied horizontal force of 135 N. If the coefficient of friction between box and floor is 0.300, find the following.
(a) the work done by the applied force
  J
(b) the increase in internal energy in the box-floor system due to friction
  J
(c) the work done by the normal force
  J
(d) the work done by the gravitational force
  J
(e) the change in kinetic energy of the box
  J
(f) the final speed of the box
  m/s

Elena · Accepted Answer

m=39.0 kg s=4.5 m, F=135 N, μ=0.3 (a) W(F) = Fs (b) ΔU= W(fr) = μmgs (c) W(N) = 0 (d) W(mg) = 0 (e) KE=W(F) –W(fr) =Fs - μmgs (f) KE=mv²/2 v= sqrt(2•KE/m)