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Energy Problem
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by ikimonokagari
on 2008-11-08 08:44:46
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If this is a easy question to you, then could you help me with this? A vertical spring has a spring constant of 850 N/m. It is compressed 0.400m when a ball is placed on it a)What is the velocity of the ball at the instance it leaves the spring? b)How high above its original position (spring compressed) will the ball fly? the answer is a)21.1m/s b)23.1m but I don't know how to get it. |
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Re: Energy Problem
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by kudoushinichi
on 2008-11-09 02:41:43
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a) is easy. Use Conservation of Energy Principle. The energy due to the compression of the spring is transferred to the ball to become kinetic energy. What's the formula for the energy stored in a compressed spring? What's the formula for the kinetic energy of a moving body? for b), you should be able to solve it once you get the initial velocity of the ball when it leaves the spring. Use one of the formulas for a body moving at a constant acceleration to solve it. This SHOULD help.
Shinjitsu wa itsumo hitotsu!
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Re: Energy Problem
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by SuicidopoliS
on 2008-11-09 04:42:46
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Seems to me that without the mass of the ball, you're not gonna very far... It's pretty clear that if the ball weights 200gr, it's gonna fly higher than when it weights 2kg. Or do i read the enunciate wrong? .oO° Life's THE CURE, the rest are details! °Oo. |
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Re: Energy Problem
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I agree with SuicidopoliS that mass needs to be specified. If it isn't, then you'd have to assume that the ball was placed onto the via the force of gravity, then you can solve for the mass using F=kx and F=mg -> kx=mg, solve for m. After that it's plug and play into the conservation on energy equations like Kudoushinichi said. However, the numbers are not the same. a) 1.98 m/s b) 0.2 m Not quite the same answers :S |
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Re: Energy Problem
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by Death Kamehameha
on 2008-11-27 00:40:33
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The mass of the ball is a very important piece of information! Without it.. There's no way you could find the correct answer! You can't use kinematics equation here for (a) as you have too many unknowns.. u,s,a and t! You would know v=0. If we have the mass, then use 'Work Energy Theorem' Where sum of work done = change in kinetic energy! which would be .5kx^2 = .5mv^2 You know k, x and m.. Find v! Use kinematics equation: a=-9.8m/s^2, v=0, u=(answer from a) find S! v^2=u^2+2aS!! Done!
-Keough- |ãŸã„ れㄠãょã†|
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