Look at the diagram below, from the frame of reference of the person riding scooter a, what is the velocity of scooter b?

you have to divide the distance over time to find the velocity

Pretend your in a car, your not moving but everything around you is.
Likewise on the scooter A, your speed is 0 but scooter's B velocity becomes 15 km/hr west.
With math: Vel_A = 5-5=0.
Vel_B = -10-5=-15 = 15 km/hr west.

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.

Answer(b) both involve the use of levers;