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    A force of (2i-j)N acts on a particle of mass 2kg. If the initial velocity of the particle is (i+3j)ms^-1, find how far it moves in the first 3 seconds.

    I've used F=ma to find the acceleration, and v=u+at to find the final velocity, but not sure where to go from here? Sorry if this is relatively simple, having to self-teach most of m1!
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    (Original post by quirksy)
    A force of (2i-j)N acts on a particle of mass 2kg. If the initial velocity of the particle is (i+3j)ms^-1, find how far it moves in the first 3 seconds.

    I've used F=ma to find the acceleration, and v=u+at to find the final velocity, but not sure where to go from here? Sorry if this is relatively simple, having to self-teach most of m1!
    v2 - u2 = 2 a s

    You have u, v and a for each component, so you should be able to calculate s (displacement) using the above equation.
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    If you don't know how to square a vector, find its magnitude and then go for v^2=u^2+2as
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    (Original post by quirksy)
    A force of (2i-j)N acts on a particle of mass 2kg. If the initial velocity of the particle is (i+3j)ms^-1, find how far it moves in the first 3 seconds.

    I've used F=ma to find the acceleration, and v=u+at to find the final velocity, but not sure where to go from here? Sorry if this is relatively simple, having to self-teach most of m1!
     s=ut+\frac{1}{2}at^2 so you don't need to find the final velocity.
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    Thanks for all your help everyone - got the right answer in the end!
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    or you could use

    s = .5( u + v )t
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    Can't say I like this question's wording.

    The displacement after 3 seconds is an appropriate question for M1, and is clearly what they meant.

    But how far it moves is asking for the length of the path traced out, IMHO, which is definitely not M1 level.
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    (Original post by ghostwalker)
    Can't say I like this question's wording.

    The displacement after 3 seconds is an appropriate question for M1, and is clearly what they meant.

    But how far it moves is asking for the length of the path traced out, IMHO, which is definitely not M1 level.
    if the acceleration is constant then it will move in a straight line ?
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    (Original post by the bear)
    if the acceleration is constant then it will move in a straight line ?
    Only if the initial velocity is zero (there may be other special cases - not checked them all out).

    In this case the displacement from t=0 onwards is (where x,y axes are the i,j components respectively):
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    (Original post by ghostwalker)
    Only if the initial velocity is zero (there may be other special cases - not checked them all out).

    In this case the displacement from t=0 onwards is (where x,y axes are the i,j components respectively):
    i see what you mean.

    if the initial velocity is in the same direction as the acceleration then it would move in a straight line.
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    (Original post by the bear)
    i see what you mean.

    if the initial velocity is in the same direction as the acceleration then it would move in a straight line.
    True. I think you've probably caught all the special cases there.
 
 
 
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