At a department store, a toy train travels on a loop of track of length 14 m. The coefficient of rolling friction between the train's wheels and the track is 0.10, and the weight of the train is 65 N. How much work does the train do against friction during each trip around the loop?

4.1 J
0 J
180 J
91 J

Question

At a department store, a toy train travels on a loop of track of length 14 m. The coefficient of rolling friction between the train's wheels and the track is 0.10, and the weight of the train is 65 N. How much work does the train do against friction during each trip around the loop?  
  
 4.1 J 
 0 J 
 180 J 
 91 J

anonymous · Answer

Because the train is moving in a closed loop, the only things that can do work are non-conservative forces.  The only one here is the friction between the wheels and track.  This is easily calculated by finding the frictional force and multiplying by the distance of the track.

Hope that helps.

akohl · Answer

Whats the equation of the friction force

anonymous · Answer

The frictional coefficient times the normal force.

akohl · Answer

I did .1*65*14 and got 91

anonymous · Answer

That is good.  And it is even one of the choices!

akohl · Answer

Thanks