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1. ### Work, Power, and Energy

Ok, then I'll give you another hint. A system is not closed if energy leaves or enters the system. In this case, no energy enters the system, but energy does leave. At the bottom of the swing, there is only one form of energy: kinetic. This can be broken up into the kinetic energy Jack is...
2. ### Work, Power, and Energy

Well, this is slightly tricky! Usually you would use conservation of energy: the sum of kinetic and potential energy remains unchanged in a closed system. The problem is that since Jack steps off, the system isn't closed! However, notice that Jack "steps" off, so he doesn't change the speed of...
3. ### Racecar travelling a banked curve

There is another equation, which it is up to you to find. This is another equation for force will also involve mass (allowing you to cancel it out). It is an equation for the force which would cause a ball to roll to the side of a tilted track.
4. ### Racecar travelling a banked curve

Here's the hint: If the car were sitting on tilted track completely still, only the friction of the wheels would keep it from sliding inwards (towards the center of the circular path). What force is acting on the car in this case? It ought to be that this force acting on the car equals the...