Sean, whose mass is 60 kg, is riding on a 5.0 kg sled initially traveling at 8.0 m/s. He brakes the sled with a constant force, bringing it to a stop in 4.0 s. What force does he apply?

130N

Explanation:

according to Newtons second law;

F = ma

F = m(v-u)/t

m is the mass = 60+5 = 65kg

v is the final velocity = 0m/s

initial velocity = 8m/s

time t = 4.0s

F = 65(8)/4

F = 65*2

F = 130N

Hence he applied a force of 130N

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.