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.

Explanation

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.