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    Hi, I seem to be struggling with a question for my maths homework. The question is:

    The formula KE=1/2mv^2 gives the kinetic energy (in joules) of an object with mass m kg and velocity v m/s.

    A) Work out the kinetic energy of a ball with mass 1.5kg, travelling at 3 m/s. (I got 27 joules, but I'm not sure if it is correct.)

    B) Draw a graph of KE against values of v between 0 and 4 m/s.

    C) What is the velocity of the ball if its kinetic energy is 9 joules?

    Thank you for any help in advance.
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    If KE= \frac{1}{2} mv^2 given the values you would do  \displaystyle \frac{1}{2} 1.5 \times 3^2 = 6.75 J
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    (Original post by B_9710)
    If KE= \frac{1}{2} mv^2 given the values you would do  \displaystyle \frac{1}{2} 1.5 \times 3^2 = 6.75 J
    Ah yes I realised my mistake, can you please help with parts B and C. Thank you for the help
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    Also for B
    Notice that KE  \propto v^2 meaning that it's a squared relationship between kinetic energy and speed. So what shape would this graph be?
    For C you have the mass and kinetic energy, so just rearrange for v and solve.
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    (Original post by B_9710)
    Also for B
    Notice that KE  \propto v^2 meaning that it's a squared relationship between kinetic energy and speed. So what shape would this graph be?
    For C you have the mass and kinetic energy, so just rearrange for v and solve.
    Would the graph be a parabola shape because of v being squared.
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    (Original post by Fhb2001)
    Would the graph be a parabola shape because of v being squared.
    Yes.
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    (Original post by Fhb2001)
    Would the graph be a parabola shape because of v being squared.
    Yes
    Very good.
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    Oh and for part C I got 2. But I'm still a little bit confused on B
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    (Original post by Fhb2001)
    Oh and for part C I got 2. But I'm still a little bit confused on B
    If you're still unsure about B, draw up a table and make data points and then plot them on a graph and you will see it to be a parabola (obviously only in the positive direction).
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    (Original post by B_9710)
    If you're still unsure about B, draw up a table and make data points and then plot them on a graph and you will see it to be a parabola (obviously only in the positive direction).
    Okay thank you for your help.
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    (Original post by Fhb2001)
    Oh and for part C I got 2. But I'm still a little bit confused on B
    Your answer for C isn't quite right. Care to post your workings?
    Remember if KE=9 J
    Then  \frac{1}{2} \times 1.5 \ v^2 = 9 .
    So just rearrange this.
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    (Original post by B_9710)
    Your answer for C isn't quite right. Care to post your workings?
    Remember if KE=9 J
    Then  \frac{1}{2} \times 1.5 \ v^2 = 9 .
    So just rearrange this.
    Is the answer close to 3.45.
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    (Original post by Fhb2001)
    Is the answer close to 3.45.
    Yes answer is  \sqrt{12} \approx 3.464 .
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    (Original post by B_9710)
    Yes answer is  \sqrt{12} \approx 3.464 .
    Okay thank you for your help. I understand B now as well.
 
 
 
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