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  1. #1
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    physics help...

    i don't know how to solve this problem..

    a box (m=30kg) is sliding along a path with initial speed of 5m/s. using the definition of energy and work determine how far the box will go before stopping. (uk=0.04)
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  2. #2
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    Quote Originally Posted by maeca View Post
    i don't know how to solve this problem..

    a box (m=30kg) is sliding along a path with initial speed of 5m/s. using the definition of energy and work determine how far the box will go before stopping. (uk=0.04)
    Lets also assume that gravitational acceleration is g = 10 m/s/s.

    So the initial kinetic energy of the box is

    E = \frac{1}{2}mv^2 = \frac{1}{2}\times 30 \times 5^2 = 375 Nm

    The frictional force opposing motion is

    F_f = \mu_k mg = 0.04 \times 30 \times 10 = 12 N

    So the work done by friction to overcome the initial kinetic energy is

    W = F_f d

    where d is the distance oevr which the force has acted. To stop the box the W = E, therefore

    d = \frac{E}{F_f} = \frac{375}{12} = 31.25 m

    Hope this helps.
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  3. #3
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    thanks..that a great help
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