Accelerations without friction problem

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The discussion focuses on solving an acceleration problem involving two blocks connected by a string, first without friction and then with kinetic friction. The initial acceleration calculated without friction is 5.0 m/s², but the user struggles to reconcile this with the lower acceleration of approximately 0.66 m/s² when factoring in friction. The correct approach involves calculating the force of friction and adjusting the equations accordingly, leading to a revised acceleration of about 0.687 m/s². The conversation emphasizes the importance of understanding the role of tension and friction in the system. Overall, the user seeks clarification on their calculations and appreciates the assistance received.
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I seem to be having some problems solving this. First of all, I figured out what the acceleration of the blocks would be without friction. I'm not sure if this is correct or not but I found that a = 5.0 m/s/s. I did this by using
Fp - Tension = ma and,
T = ma.

Then I factored in kinetic friction and I am getting ~.66 m/s/s using the same two equations except subtracting u*m*g from the left of each equation. That's not correct, is it? Going from 5 to less than 1 seems wrong to me.. Anyone know what I'm doing wrong?
 
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You sould find the force of friction because that's what pulling the block back. When 2 block are connected with strings, the tension in the string between the boxes wouldn't matter anymore. ust assume it as if it's one big chunk of block wwith mass of 30 kg.

Then you find that Fp - Ff = ma

You should get something about 0.687 m/s2
 
Thank You

I have been working on that problem for hours! Thank you!

:smile:
 
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