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    relate the changes in gravitational potential energy to changes in kinetic energy.
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    How do i do that though


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    Change in GPE=Change in KE
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    I don't understand


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    Your picture is not showing and i don't understand most statements in physics could you give me a formula or something which i could use
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    (Original post by Hollybollybee109)
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    Set potential energy (mgh) equal to kinetic energy (1/2mv^2) and rearrange for v.


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    If you mean to do this is doesnt give the right answer


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    (Original post by Hollybollybee109)
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    If you mean to do this is doesnt give the right answer


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    Also btw for future reference the masses cancel out so it should actually be v=sqrt2xgh
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    So i actually got one of my friends who do mechanics solve and they got 22. Something is that along the right line?
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    It gives the same wrong answer... I need help


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    (Original post by Hollybollybee109)
    It gives the same wrong answer... I need help


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    Is the answer 22. Something?
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    For a the answer is 18.8 and for b the answer is 9.9


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    This is what I got. Hope it's right and I didn't waste my time lol.


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    Ignore it's wrong I didn't see that it started off at 12 m/s.


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    I dont understand why the answers are that Name:  image.jpg
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    My teacher gave me the answers so maybe she got it wrong, thank you for your help


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    (Original post by Hollybollybee109)
    My teacher gave me the answers so maybe she got it wrong, thank you for your help


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    I think 22.3 is correct, both my friends who studied mechanics and I (who did a level physics) got the same results. Please do update me im really curious as how the answer is 18 x
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    (Original post by Hollybollybee109)
    My teacher gave me the answers so maybe she got it wrong, thank you for your help


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    Yeah I have no idea how to do it, sorry. I tried using momentum, energy equations and kinematics.


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    (Original post by Hollybollybee109)
    For a the answer is 18.8 and for b the answer is 9.9


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    I think I may know how your teacher arrives the "answer" of 18.8 m/s at Y.

    I suggest that you attempt to understand the statements in physics instead of just the formula or equations to use.

    Using conservation of energy and consider roller-coaster and Earth as the system.

    PE at X + KE at X = PE at Y + KE at Y
     mgh_X + \frac{1}{2}mv_X^2 = mgh_Y + \frac{1}{2}mv_Y^2 ---(1)

    It can be simplified to

     v_Y =\sqrt{ 2g(h_X - h_Y) + v_X^2} ---(2)

    If equation (2) is used, the answer would 22.3 m/s as shown below:

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    Your teacher's answer did not consider the speed at X. If the speed at X is zero, we would arrive 18.8 m/s for the speed at Y using equation (2) as shown below:
    Attachment 579632579634

    But the question stated that the speed at X is 12 m/s, so your teacher answer is incorrect.

    Similarly, we would arrive the speed at Z to be 9.9 m/s using equation (2) and consider the speed at X to be zero. Test it yourself.

    It may be good that you inform your teacher privately.
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