Laws Of Motion Question 421
Question: Two masses $ m _{1} $ and $ m _{2} $ which are connected with a light string, are placed over a frictionless pulley. This set up is placed over a weighing machine, as shown. Three combination of masses $ m _{1} $ and $ m _{2} $ are used, in first case $ m _{1}=6kg $ and $ m _{2}=2kg, $ in second case$ m _{1}=5kg $ and $ m _{2}=3kg $ and in third case $ m _{1}=4kg $ and $ m _{2}=4kg $ . Masses are held stationary initially and then released. If the readings of the weighing machine after the release in three cases are$ W _{1},W _{2} $ and $ W _{3} $ respectively then:
Options:
A) $ W _{1}>W _{2}>W _{3} $
B) $ W _{1}<W _{2}<W _{3} $
C) $ W _{1}=W _{2}=W _{3} $
D) $ W _{1}=W _{2}<W _{3} $
Show Answer
Answer:
Correct Answer: B
Solution:
[b] Reading of the weighing machine $ =2T+ $ weight of the machine.
As weight of the machine is constant. $ T=\frac{2m _{1}m _{2}}{m _{1}+m _{2}} $
So reading is maximum for the case $ m _{1}m _{2} $ is maximum as $ m _{1}m _{2} $ in all cases is same.
