An Electric Pickup Truck Really Could Pull a Freight Train—Here's How
An Anonymous Coward writes:
https://www.wired.com/story/electric-ford-f150-pulls-a-train-friction-physics/
In a recent stunt, a Ford crew hitched an all-electric F-150 pickup truck to a freight train filled with 42 more F-150s. Then a driver hit the throttle, and the pickup truck towed the 1.3 million-pound train. This raises some interesting questions. How hard is it for a truck to pull a train? Is that even possible? Could a normal truck do this? Of course it's an impressive feat-but the real limiting factor is friction.
Let's start with a more idealized situation. That's what we do in physics-when something is potentially complicated, we make the scenario less complicated to make sure we are on the right track.
So, what would it take to pull a giant train in the case of zero friction? The answer is that any tiny force would move the train. Even an ant could move it. Yes, this is true-it just seems impossible because you've never encountered a situation with zero friction.
[...] If I put in a truck coefficient of friction of 0.7 and the masses of both the truck and the train, then the coefficient of friction between the train and the rails would have to be as low as 0.0049. Yes, that's tiny. But really, trains need to have low friction. That's what makes them so awesome and able to transport massive amounts of cargo over great distances. But could any truck do this train pull? Based on this calculation, it's all about the mass of the pulling vehicle and the friction between the tires and ground. So just about any truck could do this.
Oh, what about torque and power and stuff like that for the electric F-150? Yes, you need that too. But if you don't have friction, you don't have anything. Also, here is one of my favorite demos. Even a child can move a heavy car. Here is my daughter (when she was only 7) pulling the family car.[*] If you get low enough friction you can get anything to move.
[*] http://www.youtube.com/watch?v=CbTCW9CVHLA
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