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Homework Help: A few questions

  1. May 22, 2008 #1
    I have a packet that I really need to turn in soon. It's based on a trip to an amusement park, but I couldn't go, so I need some help. If someone can help me out with any of these questions tonight or tomorrow morning before 7:00 AM Pacfic, that would be great.

    Also, some of the questions are conceptual, so I may deviate from the template for just those ones.

    Question #1

    1. How do you solve for speed using conservation of mechanical energy? The only variable given is the vertical distance - 52 meters.

    2. Relevant equations: That's what I want to know! Just knowing what to use to solve this problem would help a lot.

    3. The attempt at a solution: Don't even know where to start, I'm afraid. I'm not looking for an answer, just how to set the problem up.

    Question #2

    1. How do you calculate the length of a pendulum when given time (22 s) and number of cycles (3)?

    2. Relevant equations: None given.

    3. The attempt at a solution: I calculated frequency (at .14 hz) and period (at 7.3 s). I don't know if either of those are right, but either way, I don't know what to do next to find length.

    Conceptual Questions:

    -"Where on a roller coaster may you feel like you're being lifted out of your seat? Why?" I haven't ridden a roller coaster in a long time, so I just can't picture this sensation. Any ideas?

    -Does free fall have a constant value? I have to compare the speed of a descent to the speed of free fall, but I don't know the latter. For some reason, I think it might be a constant value (9.6 sounds familiar). Is that correct?

    -"How do bumper cars get their energy?" I put that it has something to do with the metal floor and the antenna, but I have a feeling that isn't right.

    -Speaking of bumper cars, when they collide, do they bounce back at the same speed as before or a reduced speed? I put that it was the same, but I want to check for verification.

    EDIT: Of course, I don't expect any one person to help me with all of these. Any contribution at all would be great. Thank you. :)
    Of the 40 problems we have, these are the only 6 I'm struggling with.
    Last edited: May 22, 2008
  2. jcsd
  3. May 23, 2008 #2
    Q1: I am guessing something is dropped from 52m, The potential energy at the top is equal to the kinetic at the bottom. You should have expressions that give you the value for each.

    Q2: Period is the time you add to go from one position, back to the position again. Units are in time per oscillation. An equation you should know: Period = 2*pi*sqrt(l/g)

    As far as the rest, spend some time reading your textbook, you are missing some very basic concepts about acceleration.
  4. May 23, 2008 #3
    As for the first two you should really type out the full questions...

    The conceptual questions in order:

    -Think about the forces involved when you go over a hill on a roller coaster; what happens to the direction of the forces when the car changes directions? How does the car physically keep you accelerating at its speed and from flying off?

    -I don't quite understand what you are looking for here...

    -Not sure how complete an answer you are looking for but Google will give you whatever you need. Oh and those 'antennae' are actually electrical contacts to the ceiling.

    -Think about the differences between 'perfect' mathematical situations and real world friction, sound, heat, and deformation filled situations.

    Best of luck, hope this helps!
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