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    couple of M1 q's for pos rep thanks

    edexcel M1 p104 question 2

    2.)a car of mass 850 is towing a caravan of mass 550 along a level road. the engine of the car exerts a 4ward force of 2kN. the resistance to the motion of the car and caravan are proportional to there masses eg k x their masses, where k is a constant. given that the car accelerates at 0.5 ms-2 find the tension in the tow-bar

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    take free-body diagram:
    forces on car are:
    2000N forward and k.850 backward
    2000 - 850k - T = 0.5x850

    and forces on caravan are:
    T - 550k = 0.5x550

    add them together:
    2000 - 850k - T + T - 550k = 0.5 (850+550)
    find k, then substitute in one of the equations and get T.
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    Using F=ma for;

    Car:
    2×103–T–850k = 850×0.5
    2000–T–850k = 425 (1)

    Caravan:
    T – 550k = 550 × 0.5
    T – 550k = 275 (2)

    (1)+(2)
    1400k = 2000 – 700
    1400k=1300
    14k=13
    k=13/14

    Sub k=13/14 back into (2)

    T-550(13/14)=275
    T- 7150/14=275
    T=275+ 7150/14
    T=785.7N
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    using f=ma for car:

    2000-850k-T=850*0.5
    2000-425-850k=T
    T=1575-850k................. [1]

    using f=ma for caravan:

    T-550k=550*0.5
    T=550k+275 ................. [2]

    sub. for T:

    1575-850k=550k+275
    1575-275=55k+850k
    1300=1400k
    k=13/14

    from [2]

    T=(550* 13/14) +275
    T=785.714
    T=786 N (3s.f.)

    hope that helps! (you need to draw diagram to understand completely)
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    thansk guys much appreciated
 
 
 
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