Question

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 scale reading is

• A. both the scales read M kg each
• B. the scale of the lower one reads M kg and of upper one zero
• C. the reading of the two scales can be anything but sum of the reading will be M kg
• D. both the scales read M/2 kg.

Answer 1

The correct option is A both the scales read M kg each

Spring balance gives the measure of the $springforce$ acting on it

i.e the net $downward$ force

For the lower most spring balance the net $downward$ force is $Mg$ , the force on mass due to gravity

This is the $springforce$ of the lower spring balance with which it will be pulling the upper spring balance $downward$

Hence, for the upper one also, net $downward$ force is $Mg$

So, both the balance will read the same i.e $Mg$