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The blocks shown are released from rest with spring unstretched. Pulley & horizontal surface are frictionless. If k=400 N/m and M=4.5 kg, what is maximum extension of spring?
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 one year ago
 one year ago
The blocks shown are released from rest with spring unstretched. Pulley & horizontal surface are frictionless. If k=400 N/m and M=4.5 kg, what is maximum extension of spring? http://s3.amazonaws.com/answerboardimage/20071222120396333222723984175004973.jpg
 one year ago
 one year ago

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ShadowysBest ResponseYou've already chosen the best response.1
where are you stuck? during max extension, they are not moving. for M, \(\Sigma F_y= TF_g=0\) \(T=F_g=4.5*9.8\) for 2M, \(\Sigma F_x= TF_s=0\) \(F_s=T=4.5*9.8\) \(kx=4.5*9.8\) sub k and solve for x.
 one year ago

VincentLyon.FrBest ResponseYou've already chosen the best response.0
Hi! Careful: this assumption is not correct: "during max extension, they are not moving. for M, \(\Sigma F_y= TF_g=0\)" Velocity is zero, but they are accelerating, so \(\Sigma F_y\) is not zero. Best way to solve this problem is to use conservation of mechanical energy.
 one year ago

ShadowysBest ResponseYou've already chosen the best response.1
ah. missed that. sorry. i was thinking that it was not SHM
 one year ago

ShadowysBest ResponseYou've already chosen the best response.1
by the conservation of ME, since there is no potential energy, or kinetic energy, and setting that height of M as 0 at the very beginning, and that at the max extension, the velocities are zero, i.e. still no kinetic energy, \(0=\frac{1}{2} kx^2 + MgX\) sub it all in and this should do it.
 one year ago
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