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Math Help - Dynamics 2

  1. #1
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    Post Dynamics 2

    Hello Everyone, please help me on this dynamics questions!

    A boy pulls a sled across ice by exerting a force of F kg wt. The mass of the sled is m kg, the friction between sled and ice is negligible but the sled is subject to air resistance in kg wt of magnitude k times the speed. If the sled starts from rest find expressions for:
    i) Velocity as a function of time
    and
    ii) Displacement as a function of velocty
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  2. #2
    Flow Master
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    Quote Originally Posted by Modernized View Post
    Hello Everyone, please help me on this dynamics questions!

    A boy pulls a sled across ice by exerting a force of F kg wt. The mass of the sled is m kg, the friction between sled and ice is negligible but the sled is subject to air resistance in kg wt of magnitude k times the speed. If the sled starts from rest find expressions for:
    i) Velocity as a function of time
    and
    ii) Displacement as a function of velocty
    F_{net} = ma = F - kv \Rightarrow a = \frac{F - kv}{m} \Rightarrow \frac{dv}{dt} = \frac{F - kv}{m}.

    i) Solve \frac{dt}{dv} = \frac{m}{F - kv} for v, subject to v = 0 when t = 0.

    ii) Solve \frac{dx}{dt} = v for x, subject to x = 0 when t = 0.
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  3. #3
    Grand Panjandrum
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    Quote Originally Posted by Modernized View Post
    Hello Everyone, please help me on this dynamics questions!

    A boy pulls a sled across ice by exerting a force of F kg wt. The mass of the sled is m kg, the friction between sled and ice is negligible but the sled is subject to air resistance in kg wt of magnitude k times the speed. If the sled starts from rest find expressions for:
    i) Velocity as a function of time
    and
    ii) Displacement as a function of velocty
    Go back to your teacher and tell them to get a different text book or problem set. The unit of force in SI is the Newton (a force which will accellerate a mass of 1 kg at 1 m/2^2) not a kg weight or force.

    CB
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