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ritik.dutta3
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Homework Statement
The two blocks in an Atwood machine have masses 2 kg and 3 kg. Find the work done by gravity during the fourth second after the system is released from rest.
Homework Equations
Work done by gravity= mgh
The Attempt at a Solution
Both the masses will have the same acceleration 'a'. Let T be the tension in the string.
m1= 2 kg, m2= 3 kg, g= 10 m/s^2
T-m1g=m1a
therefore, T- 20= 2a
m2g- T= m2a
therefore, 30 - T= 3a
on solving both the equations, a= 2 m/s^2
distance traveled by the blocks would be 1/2(at^2). So, the heavier block would travel 16 m downwards and the lighter block 16 m upwards.
Net mass= 3-2= 1 kg
hence, the work done should be
W= mgh= 1 x 10 x 16 = 160J
but the answer is 67J.
where am I going wrong?