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Acceleration, velocity, etc. on the Giant Drop

  1. May 14, 2006 #1
    My school went to Physics Day at Six FLags Great America and we were asked to draw conclusions about the ride the Giant Drop. Riding the ride is not necessary for answering this question, just a knowledge of forces, etc. I have tried answering this question MANY times and it has always been wrong. To get the question correct, I have to select all of the true statements , which so far I have not.


    Consider the ride at Six Flags Great America called the Giant Drop which has a constant velocity rise to the top (62.5 meters high) and drops 40.9 meters vertically before slowing down. During the "fall," what is true about the velocity and acceleration of your breakfast (in your stomach while riding the Giant Drop), and what are the forces on it? ?

    Your stomach puts a downward force on your breakfast
    Gravity puts a downward force on your breakfast.
    Your stomach puts an upward force on your breakfast.
    Gravity puts an upward force on your breakfast.
    There is only one force on your breakfast.
    There are two forces on your breakfast.
    There are three forces on your breakfast.
    The forces on your breakfast are balanced.
    The net force on your breakfast is in the downward direction.
    The net force on your breakfast is in the upward directioin.
    The acceleration is constant and positive.
    The acceleration is constant and negative.
    The acceleration is nearly zero.
    The acceleration is changing to become more positive
    The acceleration is changing to become more negative.
    The velocity is constant and positive.
    The velocity is constant and negative.
    The velocity is nearly zero.
    The velocity is changing to become more positive
    The velocity is changing to become more negative

    I have attempted this problem numerous amounts of times and I cannot arrive at the correct combination of these answers. Please help!

    IF IT HELPS, THESE ARE THE CORRECT ANSWERS TO THE SAME QUESTION, ONLY FOR THE SITUATION WHEN THE RIDE RISES TO THE TOP:
    Gravity puts a downward force on your breakfast.
    Your stomach puts an upward force on your breakfast.
    There are two forces on your breakfast.
    The forces on your breakfast are balanced.
    The acceleration is nearly zero.
    The velocity is constant and positive.
     
    Last edited: May 14, 2006
  2. jcsd
  3. May 14, 2006 #2

    Doc Al

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    Staff: Mentor

    I assume, for all practical purposes, that you (and your lunch) are in free fall during the "fall".

    Go through each of the statements and give your answer (and reasons!) why it is either true or false.
     
  4. May 14, 2006 #3
    -Your stomach puts a downward force on your breakfast- FALSE- your stomach puts an upward force on your breakfast
    -Gravity puts a downward force on your breakfast.- TRUE- gravity is a downward force
    -Your stomach puts an upward force on your breakfast.- TRUE- as stated previously, your stomach puts an upward force on your breakfast
    -Gravity puts an upward force on your breakfast.-FALSE- gravity only acts as a downward force
    -There is only one force on your breakfast.- FALSE- there are two forces, the normal force (stomach) and gravitational force
    -There are two forces on your breakfast.- TRUE- there are two forces (see above)
    -There are three forces on your breakfast.- FALSE- there are only vertical forces, and only two of them.
    -The forces on your breakfast are balanced.- FALSE- in order to be moving downward, the gravitational force has to be greater than the normal force.
    -The net force on your breakfast is in the downward direction.- TRUE- as the gravitational force is greater than the normal force and is negative, the net force should also be in the downward direction.
    -The net force on your breakfast is in the upward directioin.- FALSE- the net force in the downward direction (see above)
    -The acceleration is constant and positive.- FALSE- it is negative because if you use the formula A=F/m and the net force is negative and the mass is positive, the acceleration must be negative.
    -The acceleration is constant and negative.-TRUE- it is negative (see above)
    -The acceleration is nearly zero.- FALSE- it is accelerating
    -The acceleration is changing to become more positive- TRUE- throughout the fall, the ride should be slowing down gradually, making the negative acceleration more positive
    -The acceleration is changing to become more negative.- FALSE- it is becoming more positive (see above)
    -The velocity is constant and positive.- FALSE- the velocity is in the negative or downward direction. Also, the acceleration is negative
    -The velocity is constant and negative.- TRUE- it is negative (see above)
    -The velocity is nearly zero.-FALSE- there is velocity during the ride
    -The velocity is changing to become more positive- TRUE- it is slowing down and becoming more positive by the end of the fall
    -The velocity is changing to become more negative- FALSE- it is becoming more positive (see above)
     
  5. May 14, 2006 #4

    Doc Al

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    Staff: Mentor

    Wrong. In free fall, your stomach exerts no force on your breakfast. An example might help: Hold a rock in the palm of your hand. You hand exerts an upward force on the rock. Now jump off the roof (go into free fall). Does your hand still push up on the rock? No.
    Good.
    See above.
    Good.
    See how tricky this is? See above.
    See above.
    Certainly not three forces.
    Good.
    Good. (But what's the normal force during free fall?)
    Right.
    OK. (Assuming negative means downward.)
    Good.
    Good.
    You are only considering the "fall" portion of the ride--before you start slowing down.
    See above.
    Good.
    It's not constant.
    Good.
    Careful: Analyze the fall portion only.
    See above.
     
  6. May 14, 2006 #5
    another question: are the forces balanced once again while the ride is slowing down?
     
  7. May 14, 2006 #6

    Doc Al

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    Staff: Mentor

    Forces are only balanced if the velocity is constant. So while the ride is slowing down, forces cannot be balanced.
     
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