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← 06-33 Kinetic Energy Solution

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Showing Revision 1 created 07/23/2012 by Amara Bot.

  1. Now, you could have solve this problem using the equation of motion that we learned about in unit 2
  2. or you could have use our new super cool technique of the work energy theory,
  3. which is how I'm going to solve this one.
  4. For work energy theory, first we need the total work and that is given by this equation.
  5. Well, let's look at the forces on the ball.
  6. Well, this is an easy one, there is only gravity pointing downwards.
  7. Okay, and Δx, well, we're just going to use this distance 57 meters.
  8. W = mg * 57 and that is also equal to the change in kinetic energy.
  9. And notice that an amazing but necessary thing happens, the mass cancels out.
  10. I can also multiply both sides by 2.
  11. Oh and don't forget that the initial velocity was zero since it was released from rest,
  12. and now, we have this equation.
  13. I just take the square root of both sides, and I get the final velocity of 34 m/s.
  14. So, now, we have another tool to solve this problem.
  15. We'll find there's actually places where this tool will solve problems that our previous tools couldn't.
  16. I think I teased you a little too much when I said,
  17. I don't know what energy is, but I know what energy does.
  18. Let's dove into that a little more deeply.