- #1
solarcat
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Homework Statement
Two blocks are attached to a rope across a pulley. Block A is on the ground and has a mass of 4 kg. Block B is 2 meters above the ground and has a mass of 12 kg. When the blocks are released, block B hits the floor and block A rises to 2 meters; each block has a final speed of 4.43 m/s. Find the work done by gravity and tension for each block.
Homework Equations
Total Work = Change in kinetic energy = Work done by gravity + work done by tension
Work done by gravity = mg(Hf - H0)
The Attempt at a Solution
Block A
KE 0 = 0
KEf = (1/2) (4 kg) ( 4.43 m/s)2 = 39.2 J
Total work = KEf - KE0 = 39.2 J
Work done by gravity = 4 kg * 9.8 m/s2 * 2m = 78.4 J
Total work = work done by gravity + work done by tension
39.2 = 78.4 + Wt
Wt = -39.2 J
Similarly, Wg for block B is -235.2 J and Wt = 352.9 J
But shouldn't the work done by tension be 0 because the work done by tension on B is equal to the work done by tension on A?