Conside the fig below. A tank of water (height of water column b) is kept on a electronic weighing scale . a metal cube (side a and density D) is hung from a spring balance and the spring balance is slowly lowered into the tank till the cube reaches the bottom of tank. The distance between the bottom of the tank and the bottom of the cube at any istant is h with initially h = h° .
I have attached the figure file with this question.
So basically we need to sketch a graph between the reading of spring balance v/s h and graph between electronic scale reading v/s h.
Force of buoyance = wt of water displaced
The Attempt at a Solution
The spring balance reading is mg -B (m is the mass of block. Assumed for the purpose of que. Not given. B is force of buoyancy. No problems here.
The problem is with electronic scale reading. It will be equal to the total downward force on the container bottom right? I thought that it should be w +mg -B (w is wt of water in the container).si this should be the reading of the scale. But the ans key I got States that the reading should be mg +B. How is it so?
We also have a sub que asking us to plot the graph of sum of readings of electronic scale and spring balance.which in ans is given as straight line parallel to X axis. Of course going by the ans key , the sum is2mg. But I don't understand how is the electronic scale reading mg +B. Or is the ans key wrong?
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