1.

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 5 kg and 2kg masses.

Answer»

Solution :The masses will be lifted if the tension in the STRING is greater than the gravitational pull on masses.
Weight of 5kg mass `=5xx10=50N` and that of

2kg mass `=2xx10=20N`. From free body diagram `50 - 2T = 0` or T = 25 N (`because` pulley is massless) Tension in each string = 25 N. 2kg weight will be lifted.But 5kg weight can not be lifted ACCELERATION of 2kg weight :
`rArr 25-20=2a` or `a=(5)/(2)=2.5 ms^(-2)`
as the 5kg mass does not lifted, so its acceleration is zero.


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