Question

System shown in figure is in equilibrium and at rest. The spring and string are massless, now the string is cut. The acceleration of mass 2m and m just afterthe string is cut will be

• A. g/2 upwards, g downwards
• B. g upwards, g/2 downwards
• C. g upwards, g downwards
• D. 2g upwards, g downwards

Answer 1

Answer: (A)

g/2 upwards, g downwards

Answer 2

Initially under equilibrium of mass m
\hspace15mm T = mg \hspace15mm
Now, the string is cut. Therefore, T = mg force is decreased on mass m upwards and downwards on mass 2m
\therefore \hspace15mm a_m=\frac{mg}{m}=g\, \, \, \, \, \, \, \, \, \, (downwards) and
\hspace15mm a_{2m}=\frac{mg}{2m}=\frac{g}{2} \hspace15mm (upwards)