Q. A light spring balance hangs from the hook of the other light spring balance and a block of mass $M$ kg hangs from the former one. Then the true statement about the scale reading is
A) Both the scales read $M$ kg each
B) The scale of the lower one reads $M$ kg and of the upper one zero
C) The reading of the two scales can be anything but the sum of reading will be $M$ kg
D) Both the scales read $M/2$ kg
Explanation
(a) The arrangement in shown in figure
[image:5_image148.jpeg]
Now, draw the free body diagram of the spring balances and block.
[image:5_image149.jpeg]
For equilibrium of block, $T_{1} = Mg$
Where, $T_{1} = Reading\ of\ S_{2}$
For equilibrium of $S_{2},T_{2} = T_{1}$
Where, $T_{2} = Reading\ of\ S_{1}$
For equilibrium of $S_{1},T_{2} = T_{3}$
Hence, $T_{1}, = T_{2} = Mg$
So, both scales read M kg.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.