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Two blocks of masses 2kg and 5kg are at ...

Two blocks of masses 2kg and 5kg are at rest on ground. The masses are connected by a string passing over a frictionless pulley which is under the influence of a constant upward force F = 50 N. Find the accelerations of 5kg and 2kg masses.

Text Solution

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The masses will be lifted if the tension in the string is greater than the gravitational pull on masses.
Weight of 5 kg mass =
`5 xx 10 = 50 N` and that of
2kg mass `=2 xx 10 = 20 N`
From free body diagram
50-2T =0 or T = 25 N
(`therefore` pulley is massless)
Tension in each string = 25N. 2kg weight will be lifted. But 5kg weight can not be lifted. Acceleration of 2kg weight 25-20 = 2a or `a=5/2 = 2.5 ms^(-2)` as the 5 kg mass does not lifted, so its accleration is zero.
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