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M1 Combining forces Watch

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    Each of two forces has magnitude X N, and the resultant of these two forces has magnitude 12 N. When the magnitude of one of the forces is increased by 70%, the magnitude of the resultant of the two forces becomes 21N. Find X and the angle between the two forces.


    I really have no idea what to do here. Completely stuck. Help appreciated.
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    Diagram would be useful.

    Apply the cosine rule in each case to get two simultaneous equations.
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    (Original post by ghostwalker)
    Diagram would be useful.

    Apply the cosine rule in each case to get two simultaneous equations.
    Thanks! I drew a few diagrams but didn't think to use the cosine rule.

    In an exam, would it matter whether I chose to answer a question by constructing a force diagram or by splitting and combining components (if the question doesn't explicitly state which method to use)?

    Or is this something which would depend on the board?
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    (Original post by Julii92)
    In an exam, would it matter whether I chose to answer a question by constructing a force diagram or by splitting and combining components (if the question doesn't explicitly state which method to use)?

    Or is this something which would depend on the board?
    Years since I did A-levels, so can't give a definitive answer.

    But, it seems reasonable that you can use what ever method you like, if the paper doesn't specify.
 
 
 
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