The work done in moving a body of mass 4 kg with uniform velocity of 5 ms-1 for 10 seconds on a surface of μ = 0.4 is (take g = 9.8 m/s2 )

Force to be applied (against friction),         F = μmg = 0.4×4×9.8 = 15.68 NDisplacement, s = vt = 5 × 10 = 50 m/s          Work = Fs = 15.68 ×50 = 784 J