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grepory
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Homework Statement
In the figure, the pulleys and the cords are light, all surfaces are frictionless, and the cords do not stretch.
(a) How does the acceleration of block 1 compare with the acceleration of block 2? (Use a_2 for a2.)
(b) The mass of block 2 is 1.22 kg. Find its acceleration as it depends on the mass
m1 of block 1. (Use m_1 for m1.)
(c) Evaluate your answer for m1 = 0.537 kg. Suggestion: You may find it easier to do part (c) before part (b).
(d) What does the result of part (b) predict if m1 is very much less than 1.22 kg?
(e) What does the result of part (b) predict if m1 approaches infinity?
(f) What is the tension in the long cord in this last case?
(g) Could you anticipate the answers (d), (e), and (f) without first doing part (b)? Explain your answer.
Homework Equations
F = ma
The Attempt at a Solution
Alright.. so here's my force diagram.
http://binary-snobbery.com/pics/physics09072009.jpg
I labelled all of the tensions the same, because... I don't know. I just figured they'd all be the same... with the exception of the 2T which is just T+T.
A/B) a1 = 2a2. I don't really know why, but it was my best guess, because m2 has 2T acting as an opposing force to its natural tendency toward motion.
C) I tried this:
m1:
[tex]\Sigma[/tex] Fx = T = m1a1
m2:
[tex]\Sigma[/tex] Fy = 2T - m2g = m2a2
So then I used the identity found in part A to solve the system for a2.
2(m1a1) - m2g = m2a2
2(m1(2a2)) - m2g = m2a2
4m1a2 - m2g = m2a2
Do a little algebra and you end up with:
a2 = m2g / 4(m1 - m2)
I plugged in the given values, but I got the wrong answer. That's basically where I gave up. I am missing something fundamental, I guess.
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