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Edited by Kerrah:
2/11/2013 11:26:56 PM
10
Maths (Mechanics Help)
[url]http://i49.tinypic.com/2vvmlbt.jpg[/url]
I'm stuck on these questions based on inclined planes and pulley systems z.z
I'm ok with question 1 on impulses and change in momentum, but the rest is just gwaah.
Help would be appreciated
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This smells of the Leaving Certificate...
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Edited by Trollheim: 2/12/2013 12:05:15 AMOk Part E, ok, when P hits the ground, Q is still moving upward. The problem then becomes like throwing a ball up in the air - the ball goes up, and then must come back to where it started. The left mass hit the ground at 1.5 seconds, so the right mass becomes a ball thrown up in the air at 1.5 seconds. It had been accelerated at a rate of 2.8 m/s^2 for 1.5 seconds, so we need to calculate its velocity. Once we know its velocity, it simply becomes a problem of determining how long the ball is in the air. (What I had before about determining velocity I believe is wrong, I don't remember the equation off the top of my head and don't want to confuse you with calculus, look the formula up yourself).
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Edited by Trollheim: 2/11/2013 11:54:57 PMPart E... eh. I'll have to think about that a little bit. (added units to the solutions below)
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Finally, part D, you used the information that the string can't stretch to determine the tension within the string.
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Edited by Trollheim: 2/11/2013 11:54:34 PMSince the left mass is accelerating at 2.8 m/s^2, the right mass is accelerating at -2.8 m/s^2. MA = Fg - Ft... but A is negative, so flip Ft and Fg. Ft - Fg = MA. You know Ft now, Fg is 9.8*M. You need to use algebra to isolate the M. A is 2.8. M(A + 9.8) = Ft. Ft is 3.5, so M = .27777, which is 5/18 kg.
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Edited by Trollheim: 2/11/2013 11:47:41 PMTension in the string... MA = Fg-Ft You know A is 2.8, M is .5, Fg is 4.9 (9.8*.5), solve for Ft. Ft is 3.5 Newtons.
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[url]https://www.khanacademy.org/science/physics/forces-newtons-laws[/url] This should help.
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Edited by Trollheim: 2/11/2013 11:54:26 PMPart A is a basic acceleration velocity distance equation. 1/2 a t^2 = X where x is 3.15 and t is 1.5 A is 2.8 m/s^2.
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1+1=11? You're -blam!-ed dude.
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Physics. Lemme take a look.
