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Thread: have i got the units right in this calculation?

  1. #1 have i got the units right in this calculation? 
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    Hi all. I have been given the following and am not confident i have got the units correct so was hoping someone could help me.

    d.The equation for a straight line is often used in science to find an unknown without reference to a graph. For a set of data for two quatities, A and B, where A is plotted on the x-axis and B on the y-axis, the gradient of the straight line is 2.3 104m s−1 and the intercept on the y-axis is 5.8 104 m. Using the equation for a straight line (Book 3, Equation 7.12 ) as your starting point, determine the value for A when B = 6.2 105 m. Show all your workings and give your answer in scientific notation and to two significant figures.
    Y =mx + c

    C = 5.8 104 m
    M= 2.3 104m s−1
    B = 6.2 105 m

    6.2 105 m 2.3 104m s−1 A 5.8 104 m
    6.2 105 m - 5.8 104 m = 2.3 104m s−1 A
    620000m 58000 m s−1= 23000 m A
    562000 s = 23000m A
    562000s = A
    23000m
    24.434782608695652173913043478261s = A
    A = 24s to 2 significant figures.


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  3. #2  
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    Quote Originally Posted by studley89 View Post
    Hi all. I have been given the following and am not confident i have got the units correct so was hoping someone could help me.

    d.The equation for a straight line is often used in science to find an unknown without reference to a graph. For a set of data for two quatities, A and B, where A is plotted on the x-axis and B on the y-axis, the gradient of the straight line is 2.3 104m s−1 and the intercept on the y-axis is 5.8 104 m. Using the equation for a straight line (Book 3, Equation 7.12 ) as your starting point, determine the value for A when B = 6.2 105 m. Show all your workings and give your answer in scientific notation and to two significant figures.
    Y =mx + c

    C = 5.8 104 m
    M= 2.3 104m s−1
    B = 6.2 105 m

    6.2 105 m 2.3 104m s−1 A 5.8 104 m
    6.2 105 m - 5.8 104 m = 2.3 104m s−1 A
    620000m – 58000 m s−1= 23000 m A
    562000 s = 23000m A
    562000s = A
    23000m
    24.434782608695652173913043478261s = A
    A = 24s to 2 significant figures.
    The problem is much simpler than what you made out. The question is: when Y = B, what is X (=A)?

    A = (B-C)/M. Your answer is correct.


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  4. #3  
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    Thank you, i'm still finding it pretty confusing so your feedback is much appreciated!
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  5. #4  
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    Quote Originally Posted by studley89 View Post
    Thank you, i'm still finding it pretty confusing so your feedback is much appreciated!
    The original statement is y = mx + c, so elementary algebra gives x = (y-c)/m.
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