a vertical pulley has a radius of 5 cm. A thin string is wound around the outside of the pulley, and a weight of 8 N is suspended from it. The pulley has a brake, located 3 cm from the pulley's axle. how much force must the brake exert to keep the pulley from turning?

Wish i knew this to !

The answer is frictional force

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.

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