- #1

Claus Berner

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## Homework Statement

What is the maximum acceleration the train can achieve?

Engine effect=6500kW

μ(Friction Coefficient (between rails and wheels))=0.45

g=9.82N/kg

m(Train weight)=120,000kg

α=0

## Homework Equations

F

_{μ}=F

_{n}*μ

F

_{n=cos(α)*m*g a=F/m The Attempt at a Solution We've used the equations for objects, to determine the amount of force is needed to move. F>Fμ if the object is to move. But for an object, a higher friction coefficient means the need for more force to pull. Therefore, a higher friction at constant force, means lower acceleration. But for vehicles, a higher friction means a higher acceleration, because it can convert more of it's rotational energy to translational energy. I asked my teacher, but he explained that when the train is moving the friction force, must be the same as the trains forward force. Therefore the maximum acceleration becomes, the friction force divided by mass. a=Fμ/m. But in my head that's a very oversimplified explanation, i cannot see the correlation to rotational mechanics and the friction between rails and wheels. In my head the friction describes how much of the engine power can be converted to translational energy, and that the limit of the force is due to the fact that maybe if you use more force than the friction force, then the wheels will simply spin without grip. I feel like I'm missing something which binds these things together, but my teacher refused to tell me, or he didn't know :/}