Three identical train cars, coupled together, are rolling east at speed v0. a fourth car traveling east at 2v0 catches up with the three and couples to make a four-car train. a moment later, the train cars hit a fifth car that was at rest on the tracks, and it couples to make a five-car train. what is the speed of the five-car train? express your answer in terms of v0

V=Vo

Explanation:

Lets take all car have same mass (m).

Given that

Initial Speed of 3m mass train  = Vo

Initial Speed of m mass train  = 2Vo

Initial Speed of 5m mass train  = 0

Lets take final speed of 5m mass train = V

Initial linear momentum Pi

Pi= 3m x Vo + m x 2Vo + 5m x 0

Pi=5 m Vo

The final linear momentum Pf

Pf= 5m x V

There is no any external force that is why linear momentum will be conserved

Pi=Pf

5 m Vo=5 m V

V=Vo

The speed of the  final car will be same as initial velocity of 3m cars.

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.