Solved: PHYSICS Question for NEET

NEET PHYSICSEasy

A block of mass 4 kg is suspended through two light spring balances A and B connected in series. Then A and B will read respectively:

4 kg and 0 kg

0 kg and 4 kg

4 kg and 4 kg

2 kg and 2 kg

System Configuration: When two light (massless) spring balances are connected in series (one suspended from the other) supporting a mass, the tension is uniform throughout the chain.
Free Body Diagram:

For the block: The downward force is weight $W = mg = 4g$ . The upward force is the tension in Balance B ( $T_B$ ). For equilibrium, $T_B = 4g$ . Balance B reads $4$ kg.
For Balance B: It is massless. It is pulled down by tension $T_B$ and pulled up by tension from Balance A ( $T_A$ ). For equilibrium, $T_A = T_B = 4g$ . Balance A reads $4$ kg [Source 41].

Newton's Third Law: The action and reaction forces are equal and opposite. The force transmitted through the series of massless springs is equal to the load suspended.
Conclusion: Both spring balances measure the same tension corresponding to the mass of the block.

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