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    I've attached the question and the mark scheme. I understand everything except part d, the thing I'm most confused about is the 8/5 - I understand where the values come from but not why they're divided.

    Thanks is advance.

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    Name:  ImageUploadedByStudent Room1461578799.250818.jpg
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    (Original post by meloj)
    I've attached the question and the mark scheme. I understand everything except part d, the thing I'm most confused about is the 8/5 - I understand where the values come from but not why they're divided.

    Thanks is advance.

    Name:  ImageUploadedByStudent Room1461578775.064276.jpg
Views: 42
Size:  45.3 KB
    Name:  ImageUploadedByStudent Room1461578799.250818.jpg
Views: 37
Size:  42.3 KB



    Posted from TSR Mobile
    If B moves in the direction of 3\mathbf{i} + 4\mathbf{j} then the velocity must be of the form k(3\mathbf{i} + 4\mathbf{j})

    Now the magnitude of 3\mathbf{i} + 4\mathbf{j} is 5 but we need a magnitude of 8 so we need to multiply the vector by \frac{8}{5}

    This works now since the magnitude of \frac{8}{5}(3\mathbf{i} + 4\mathbf{j}) is \frac{8}{5}\times 5 = 8.
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    since the direction of B is 3i+ 4j then a unit vector of velocity in that direction would be

    {1/5}{3i+ 4j}.... this means the speed would be 1 m/s.

    Since we want 8 m/s you multiply by 8

    =====> {8/5}{3i+ 4j}
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    (Original post by notnek)
    If B moves in the direction of 3\mathbf{i} + 4\mathbf{j} then the velocity must be of the form k(3\mathbf{i} + 4\mathbf{j})

    Now the magnitude of 3\mathbf{i} + 4\mathbf{j} is 5 but we need a magnitude of 8 so we need to multiply the vector by \frac{8}{5}

    This works now since the magnitude of \frac{8}{5}(3\mathbf{i} + 4\mathbf{j}) is \frac{8}{5}\times 5 = 8.
    Thanks for your help! I understand it now
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    Thanks for your help! Much appreciated

    (Original post by the bear)
    since the direction of B is 3i+ 4j then a unit vector of velocity in that direction would be

    {1/5}{3i+ 4j}.... this means the speed would be 1 m/s.

    Since we want 8 m/s you multiply by 8

    =====> {8/5}{3i+ 4j}
 
 
 
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