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seen Nov 23 '13 at 13:42

Jan
3
comment Why does a car engine not do work if the wheels don't slip?
All I can say is wow. Do you think that it is possible for me to have such detailed understanding?
Jan
3
comment Why does a car engine not do work if the wheels don't slip?
Thank you. This is what I was searching for.
Jan
3
awarded  Scholar
Jan
3
accepted Why does a car engine not do work if the wheels don't slip?
Jan
3
awarded  Student
Jan
3
comment Why does a car engine not do work if the wheels don't slip?
It was just that. Except for the bit saying that air resistance has been neglected.
Jan
3
comment Why does a car engine not do work if the wheels don't slip?
@David: Clearly since there is a change in kinetic from 0 to K there has to be work done on the vehicle from an external force to accelerate it (friction?), but in this scenario we are deliberately told that it is 0. What's going on?
Jan
3
comment Why does a car engine not do work if the wheels don't slip?
@Skilvvz: Yes, I have realized that. The thing is that the internal friction is 0 so that can be easily discounted, like I said what I have been taught from OCW (Walter Lewin rocks) and what I have understood just doesn't add up.
Jan
2
comment Why does a car engine not do work if the wheels don't slip?
I was told that the external force was the engine (! Sounded kinda suspicious to me). Are you sure? That would make far more sense than the torturous explanations I keep on coming up with.
Jan
2
comment Why does a car engine not do work if the wheels don't slip?
What I've been taught doesn't add up. I've checked it from my book and my teacher that the question and it's answer is right. The question was; A car starts from rest and in 20 s gains a kinetic energy K. What is the work done by an external force? Perhaps, I have misunderstood the question. Or, there is something wrong in my teacher's explanation, but I am really confused. What I know and understand just doesn't add up with this. What's the truth?
Jan
2
awarded  Editor
Jan
2
revised Why does a car engine not do work if the wheels don't slip?
added 198 characters in body
Jan
2
comment Why does a car engine not do work if the wheels don't slip?
Sorry about not being clear, but I was talking about an idealised case where air resistance is negligible and the tires are perfectly rigid and there is no internal friction at play. So, then why is it 0?
Jan
2
comment Why does a car engine not do work if the wheels don't slip?
In the question there is a change in kinetic energy as the car starts from rest, but there is no air resistance. What I am trying to put into words is that by your explanation in this case the work done will be zero as the friction hasn't been overcome and there is no air drag to overcome. Hence, even though the car gains kinetic energy the work done by the engine can be said to be 0. Is that correct?
Jan
2
asked Why does a car engine not do work if the wheels don't slip?