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    A particle moving with speed Vms-1 in direction d has velocity vector v. find v
    1) V = 10, d = 3i-4j

    I'm confused on what it actually wants us to work out. Thanks
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    the V they give you is the magnitude of the velocity vector you need to find it in vector form.

    I think..
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    (Original post by thelion0)
    the V they give you is the magnitude of the velocity vector you need to find it in vector form.

    I think..
    so how would i go about working it out?
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    (Original post by physicshelpme)
    so how would i go about working it out?
    Is that all that the question asked?
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    The velocity vector is going in the same direction as the directional vector; in other words, the velocity vector is the directional vector 3i-4j multiplied by some scalar such that the magnitude of the velocity vector is V=10.

    Do you see what you need to do yet?

    Hint: What's the modulus of 3i-4j?
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    (Original post by thelion0)
    Is that all that the question asked?
    yea that was everything
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    (Original post by aznkid66)
    The velocity vector is going in the same direction as the directional vector; in other words, the velocity vector is the directional vector 3i-4j multiplied by some scalar such that the magnitude of the velocity vector is V=10.

    Do you see what you need to do yet?

    Hint: What's the modulus of 3i-4j?
    I'm not sure what modulus means?
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    (Original post by aznkid66)
    The velocity vector is going in the same direction as the directional vector; in other words, the velocity vector is the directional vector 3i-4j multiplied by some scalar such that the magnitude of the velocity vector is V=10.

    Do you see what you need to do yet?

    Hint: What's the modulus of 3i-4j?
    oooh right!! I would rep you but I can't
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    (Original post by physicshelpme)
    I'm not sure what modulus means?
    Sorry, my bad! It means the same thing as magnitude ^^;
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    (Original post by aznkid66)
    Sorry, my bad! It means the same thing as magnitude ^^;
    I don't understand, could you please explain how i'd work it out, thank you
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    So a vector is magnitude+direction. The magnitude is the distance of the vector from tip to tail. Simple pythagoras shows that for a vector a=xi+yj the magnitude denoted as |a| is sqrt(x^2+y^2).

    Vectors can be used to represent the velocity (speed+direction) of things. In this case, the speed is equal to the magnitude of this velocity vector. Thus, we know the question is asking for a vector with a magnitude of V=10.

    If you multiply d=3i-4j by any positive scalar k, then the resultant vector will be going in the same direction as d. So what we're really looking for is a vector kd such that the magnitude |kd|=10.

    The trick is to note that, if k is a scalar, |kd|=k|d|, so k|d|=10. Furthermore, since you're given d, you can find |d|=sqrt(3^2 + 4^2)=5. This leads you to k*5=10, and k=2.

    So, the answer kd is actually 2d=6i-8j.
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    (Original post by aznkid66)
    So a vector is magnitude+direction. The magnitude is the distance of the vector from tip to tail. Simple pythagoras shows that for a vector a=xi+yj the magnitude denoted as |a| is sqrt(x^2+y^2).

    Vectors can be used to represent the velocity (speed+direction) of things. In this case, the speed is equal to the magnitude of this velocity vector. Thus, we know the question is asking for a vector with a magnitude of V=10.

    If you multiply d=3i-4j by any positive scalar k, then the resultant vector will be going in the same direction as d. So what we're really looking for is a vector kd such that the magnitude |kd|=10.

    The trick is to note that, if k is a scalar, |kd|=k|d|, so k|d|=10. Furthermore, since you're given d, you can find |d|=sqrt(3^2 + 4^2)=5. This leads you to k*5=10, and k=2.

    So, the answer kd is actually 2d=6i-8j.
    thanks alot!
 
 
 
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