a block of mass m rests on a block of mass m1 which is on a tabletop. a light string passes over a frictionless pulley and connects the blocks. the coefficient of kinetic friction between the blocks and between the block of mass m1 and the tabletop is the same. a force f pulls the upper block to the left and the lower block to the right. the blocks are moving at a constant speed.

Ithink it is c ,i hope i you

stands for electromotive force and it is measured in volts. despite its name, it is not actually the force in the sense of being a "pushing" or "pulling" (not measured in newtons).an equation that relates emf,  ℰ,  to a battery's terminal voltage, v, current, i, and internal resistance, r, is    ℰ = v + irin this case, the emf can be interpreted as a voltage—a difference in electric potential.i would not say that it would be considered an energy. if emf can be defined as the energy/work per a unit charge from a battery or other electric source, then it is not strictly energy.

Ke reqd to move from 0 to 50 will be proportional to 50x50 or 2500. this is equal to w.  to change vel from 50 to 150 you need energy prop to 22500 - 2500 = 20,000. this corresponds to 8w.  best answer is a) . work reqd is prop to velocity squared.