Two blocks with different mass are attached to either end of a light rope that passes over a light, frictionless pulley that is suspended from the ceiling. The masses are released from rest, and the more massive one starts to descend. After this block has descended a distance 1.00m , its speed is 1.50m/s . If the total mass of the two blocks is 13kg, then what is:(adsbygoogle = window.adsbygoogle || []).push({});

1)the mass of the more massive block

2)the mass of the less massive block

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Since the more massive block descended 1m, then the less massive block must have ascended 1.0m. Also, since the more massive block travels at 1.50m/s, then the less massive block must trave -1.50m/s. Setting the height of the less massive block, m1, as 2.0m, and the height of the more massive block, m2, as 0, then

m1gh + (1/2)m1v1^2 = (1/2)m2v2^2

m1(gh + (1/2)v1^2) = m2(1/2 *v2^2)

m1/m2 = v2^2/(gh + v1^2)

m1/m2 = (1.125 m^2/s^2) / (20.725 m^2/s^2)

m1/m2 = 0.0543

I figured, since given only the combined mass, I had to find the ratio of the masses. I multiplied the ratio (0.0543) times 13kg, and found that m1 = 0.706kg, and 13kg - 0.706kg = 12.294kg. Not right, though. Anyone know where I went wrong?

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# Homework Help: Finding the masses of two blocks in a pulley system using work-energy theorem

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