I have posted 2 problems, 12.126 and 12.72. I have read in the book that you can assume the acceleration remains constant when the forces applied are constant.(adsbygoogle = window.adsbygoogle || []).push({});

In problem 12.126 that is the case, the weights of the blocks and the forces P and T remain constant so I assumed that the acceleration of the blocks were also constant and I solved the problem successfully.

But in problem 12.72, I obviously cannot assume the acceleration is constant, why not? I am neglecting friction and the weights of the blocks are contant, the tension in the cord is also constant, isnt it? What is the difference between these problems?

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# Assuming acceleration is constant

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