Aforce of 60. newtons is applied to a rope to pull a sled across a horizontal surface at a constant velocity. the rope is at an angle of 30. degrees above the horizontal. determine the magnitude of the frictional force acting on the sled. [1]

For this case, the friction force acting on the sled will be of the same magnitude as the horizontal component of the force that is being applied at 30 degrees above the horizontal since the velocity is constant. Therefore, the result will be given by:
 F = 60 * cos (30) = 51.96N
 the magnitude of the frictional force acting on the sled is 51.96 N

It is d, all the other ones say incorrect answer .

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.