- #1
sandyforever
- 12
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Homework Statement
Two scale-pans each of mass 3 lbs are connected by a string passing over a smooth pulley. Show how to divide a mass of 12 lbs between the two scale-pans so that the heavier may descend a distance of 50 ft in the first 5 seconds.
Homework Equations
F = ma, mg - T = ma, where, T is the tension on the string, (acceleration of the mass on one end of the string) = -(acceleration of the mass on the other end)
The Attempt at a Solution
well, in my attempt to this question, I considered the pan and the divided mass at one of the ends as a connected system of masses having a common acceleration, say, 'a' and assumed the divided masses as x and (12-x) where (12-x) is the heavier mass. Then by Newton's second law I came up with the equation : at one end, (3+12-x)g - T = (3+12-x)a and similarly for the other end. Here, I considered the downward direction as positive. Using the given data I got a = 4 ft/s^2. Anyway, after solving the force equations for both the ends and using the value of a, I got x =12/5 lbs and 12-x = 48/5 lbs. But the answer is given to be 57/8 lbs and 39/8 lbs. Please help me out.