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- Jun 30, 2014
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I came across the following question: a roller coaster starts from point A and makes a complete loop around the track until it arrives back at point A and stops. What is true regarding the work it did with respect to gravity and friction?
Is it correct to say the coaster did zero work with respect to gravity, since by ending up at the same height any positive vertical displacement was canceled out by negative vertical displacement? Or is it zero simply because initial and final position is the same?
The part that's more confusing for me is work with respect to friction. Did it do positive work against friction (since the force of the coaster was always in the same direction as the coaster's displacement) or did it do zero work because "doing work against friction" is a nonsense concept? I can understand friction doing negative work against the coaster by increasing its internal energy but how does something do work, negative or positive, against friction?
Is it correct to say the coaster did zero work with respect to gravity, since by ending up at the same height any positive vertical displacement was canceled out by negative vertical displacement? Or is it zero simply because initial and final position is the same?
The part that's more confusing for me is work with respect to friction. Did it do positive work against friction (since the force of the coaster was always in the same direction as the coaster's displacement) or did it do zero work because "doing work against friction" is a nonsense concept? I can understand friction doing negative work against the coaster by increasing its internal energy but how does something do work, negative or positive, against friction?