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Vectors Velocity Accelaration and Displacement HELP!!

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    ReputationRep:
    Hi Every1

    Got question on vectors which i cant handle, can some please show me how to go through this, thankyou!

    A body has initial velocity u ms-1 and accelerates uniformly at a ms-2 for t
    seconds, reaching a velocity of v ms-1.
    The relationship between these measures is:
    v = u + at.
    Its displacement, s metres, over this period is given by:
    s = ut + 0.5at^2

    1. A body is initially at rest and accelerates for 8 secs at

    5
    -1 ms-2
    2
    a) what is its final velocity and b) what is its displacement

    I've worked out the final velocity to be

    40
    -8
    16

    How do you work out displacement??
  2. Offline

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    (Original post by Student21)
    Hi Every1

    Got question on vectors which i cant handle, can some please show me how to go through this, thankyou!

    A body has initial velocity u ms-1 and accelerates uniformly at a ms-2 for t
    seconds, reaching a velocity of v ms-1.
    The relationship between these measures is:
    v = u + at.
    Its displacement, s metres, over this period is given by:
    s = ut + 0.5at^2

    1. A body is initially at rest and accelerates for 8 secs at

    5
    -1 ms-2
    2
    a) what is its final velocity and b) what is its displacement

    I've worked out the final velocity to be

    40
    -8
    16

    How do you work out displacement??
    What is the -8 and 16 for?
    You've also answered your question in your own post. Read it again.
  3. Offline

    ReputationRep:
    (Original post by Student21)
    Hi Every1

    Got question on vectors which i cant handle, can some please show me how to go through this, thankyou!

    A body has initial velocity u ms-1 and accelerates uniformly at a ms-2 for t
    seconds, reaching a velocity of v ms-1.
    The relationship between these measures is:
    v = u + at.
    Its displacement, s metres, over this period is given by:
    s = ut + 0.5at^2

    1. A body is initially at rest and accelerates for 8 secs at

    5
    -1 ms-2
    2
    a) what is its final velocity and b) what is its displacement

    I've worked out the final velocity to be

    40
    -8
    16

    How do you work out displacement??
    The final velocity is  40 ms^{-1} , why have you written -8 and 16 after it?

    For displacement use the formula,  s = ut + \dfrac12 at^2 , we know the acceleration, time and initial velocity so displacement can be worked out.
  4. Offline

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    (Original post by raheem94)
    The final velocity is  40 ms^{-1} , why have you written -8 and 16 after it?

    For displacement use the formula,  s = ut + \dfrac12 at^2 , we know the acceleration, time and initial velocity so displacement can be worked out.
    The question had a column vector so my answer was also a column vector. I just did not know how to put the big brackets into a html page. I've checked my answer and it is right and includes the -8 and 16. What i cannot work out is the displacement in column vector form.

    Edit ive added a pic of the question sheet Click image for larger version. 

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    Click image for larger version. 

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  5. Offline

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    (Original post by Student21)
    The question had a column vector so my answer was also a column vector. I just did not know how to put the big brackets into a html page. I've checked my answer and it is right and includes the -8 and 16. What i cannot work out is the displacement in column vector form.

    Edit ive added a pic of the question sheet Click image for larger version. 

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Views:	17 
Size:	62.2 KB 
ID:	146744
    Try to work out the displacement in the same way, first use, a=-5, then a=-1, then a=2.

    For the first row, input, a=5, t=8, in   s = ut + \dfrac12 at^2

    Find the displacement, use a similar method to find the other 2 rows.
  6. Offline

    ReputationRep:
    (Original post by Student21)
    The question had a column vector so my answer was also a column vector. I just did not know how to put the big brackets into a html page. I've checked my answer and it is right and includes the -8 and 16. What i cannot work out is the displacement in column vector form.

    Edit ive added a pic of the question sheet Click image for larger version. 

Name:	Untitled.jpg 
Views:	17 
Size:	62.2 KB 
ID:	146744
    Is the answer to this displacement part,  \displaystyle \begin{pmatrix} 160 \\ -32 \\ 64 \end{pmatrix} \ ?
  7. Offline

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    (Original post by raheem94)
    Try to work out the displacement in the same way, first use, a=-5, then a=-1, then a=2.

    For the first row, input, a=5, t=8, in   s = ut + \dfrac12 at^2

    Find the displacement, use a similar method to find the other 2 rows.
    I just found out the answers on the answer sheet are not even correct. I was getting the right answers all along. Thanks for the help anyways, it was much appreciated.

    Yes the answer you got is the correct one.

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