A horizontal force of magnitude 39.0 N pushes a block of mass 4.21 kg across a f

Question

A horizontal force of magnitude 39.0 N pushes a block of mass 4.21 kg across a floor where the coefficient of kinetic friction is 0.634. (a) How much work is done by that applied force on the block-floor system when the block slides through a displacement of 4.20 m across the floor? (b) During that displacement, the thermal energy of the block increases by 37.4 J. What is the increase in thermal energy of the floor? (c) What is the increase in the kinetic energy of the block? (a) Number Units (b) Number Units (c) Number Units

Explanation / Answer

a) work done by the applied force is W1 = F_applied*dispalcement = 39*4.2 = 163.8 J

b) increase in thermal energy of the floor is 37.4 +(0.634*4.21*9.8*4.2) =147.3 J

c) using work energy theorem ,

work done by the net force = change in kinetic energy

163.8 - 147.3 = change in kinetic energy

so increase in kinetic energy is 163.8-147.3 = 16.5 J

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