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person
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 Posted: Sun Mar 26, 2006 12:52 pm Post subject: physics question about forces |
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If the speed of the box on the bottom is v. The box must do work to get to the top (working againts gravity). Thus, the work done should be W = F*d. When it gets to the top, the potential energy, rises from 0 to Ep = m*g*h. So, wouldn't the Ek = 1/2mv^2 = W + Ep = F*d + m*g*h? But that doesnt make sense since we learnt that Ek = Ep. So why is this wrong?
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Cervantes
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| Posted: Sun Mar 26, 2006 2:46 pm Post subject: (No subject) |
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The work you do to push the box to the top of the ramp is equal to the gravitational potential energy at the top of the ramp.
Once you've pushed the box up to the top, you cannot harvest both the work you did AND the gravitation potential energy, for they are one and the same thing. |
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1of42
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| Posted: Sun Mar 26, 2006 4:20 pm Post subject: (No subject) |
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| Neglecting friction and air resistance? |
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MysticVegeta
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| Posted: Sun Mar 26, 2006 4:27 pm Post subject: (No subject) |
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I guess neglecting both factors cause otherwise its complex calculations.
The Ek decreases as the box reaches the top. But their sum (Mechanical Energy is always constant at any given postion) |
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