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Math Help - Force

  1. #1
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    Force

    A tractor of mass 1000 kg tows a trailer of mass 1000kg . The total resistance is 4000 N and is constant . One quarter of the total resistance acts on the trailer . Initially the acceleration of both the tractor and trailer is 2.0 m/s^2 . Finally , both of them move with the same uniform speed of 6.0 m/s . What is the force on the tractor along the tow-bar when

    (a) acceleration is 2.0 m/s^2

    (b) the tractor and trailer move at 6.0 m/s

    I need some explaination here . THanks .
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  2. #2
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    Quote Originally Posted by thereddevils View Post
    A tractor of mass 1000 kg tows a trailer of mass 1000kg . The total resistance is 4000 N and is constant . One quarter of the total resistance acts on the trailer . Initially the acceleration of both the tractor and trailer is 2.0 m/s^2 . Finally , both of them move with the same uniform speed of 6.0 m/s . What is the force on the tractor along the tow-bar when

    (a) acceleration is 2.0 m/s^2

    (b) the tractor and trailer move at 6.0 m/s

    I need some explaination here . THanks .
    The horizontal forces acting on the trailer are the friction force (1000 N) and the tension force T from the tow bar. Hence Fnet = T - 1000.

    But Fnet = ma = (1000)(a). Therefore:

    (a) T - 1000 = (1000)(2).

    (b) T - 1000 = (1000)(0). Note that a = 0 since velocity is constant.
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  3. #3
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    Quote Originally Posted by mr fantastic View Post
    The horizontal forces acting on the trailer are the friction force (1000 N) and the tension force T from the tow bar. Hence Fnet = T - 1000.

    But Fnet = ma = (1000)(a). Therefore:

    (a) T - 1000 = (1000)(2).

    (b) T - 1000 = (1000)(0). Note that a = 0 since velocity is constant.

    THanks Mr fantastic . But i am a bit confused . The question asks for the force acting on the tractor . But the working in (a) seems to be the force acting on the trailer .

    Or perhaps they are equal ? THanks for explaining .
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  4. #4
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    Quote Originally Posted by thereddevils View Post
    THanks Mr fantastic . But i am a bit confused . The question asks for the force acting on the tractor . But the working in (a) seems to be the force acting on the trailer .

    Or perhaps they are equal ? THanks for explaining .
    The forces are equal in magnitude and opposite in direction (see Newtons Third law).
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