Question

A 0.5 kg block of iron is pushed 2 m across a level table where there is a coefficient of friction is 0.4. The specific heat of iron is 449 J/kg0C. How much work was done by friction?

Answer 1

Well,here we can apply that amount of force which is necessary just to balance the frictional force,and i.e obviously equals to the magnitude of the frictional force,so that the block will move with constant velocity.

So,here maximum frictional force(`f`) acting on the moving object is `mu * N=mu mg = 0.4*0.5*9.8=1.96N` (`mu` is the coefficient of friction)

So,work done by frictional force in moving the object by `2 m` will be `f*s = 1.96*2=3.92 J`

Sorry,but nowhere I found the use of given specific heat of iron in this problem,as no statements about energy loss by means of heat heat production or something associated to that is mentioned.