Jasminebunnies
Conservation of Mechanical Energy:
A pendulum bob is released from some initial height such that the speed of the bob at the bottom of the swing is 1.9m/s. What is the initial height of the bob?
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imron07
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|dw:1349481173829:dw|
Jasminebunnies
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Why would K(A) be 0?
imron07
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Yes, it 'released' without initial speed right?
Jasminebunnies
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isnt the initial speed 1.9 m/s?
imron07
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No, that's the speed at B.
Jasminebunnies
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oh ok so you got the zero from A?
imron07
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Yup :)
Jasminebunnies
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but the book says tha answer is 0.18m but how would you get that answer?
Jasminebunnies
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*the
imron07
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I got the same answer. I wrote the formula at the picture:\[h=\frac{v^2}{2g}\]
Decart
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when it comes to a pendulum does it not depend on the lenght of the string?
Decart
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U=mgl
Jasminebunnies
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ok, so you would use that formula, h=v^2/2g to get 0.18m?
imron07
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@Jasminebunnies : Yes
Jasminebunnies
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ohhh ok and the zero is put there because there is no mass?
imron07
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Omg! (^ ^!)
Which zero?
Jasminebunnies
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lol! the zero in your original equation that you said came from A, in front of mgh
imron07
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That's because v=0 at highest point.
Jasminebunnies
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ohhh ok, is that because it has not been released at that point?
Jasminebunnies
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@imron07
imron07
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Because by the time the pendulum is released, the velocity is zero. It start from rest.
Jasminebunnies
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yes, ok! thank you! I understand now :)
imron07
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ok ;)