A U-tube contains water and methylated spirit separated by mercury. The mercury in the two limbs of the tube is in level. If the water stands to a level 12.8cm above the mercury, then find the length of spirit in the U-tube. Take relative density of spirit as 0.8.
Given that, for both the limbs mercury is in level. Therefore, the pressure due to height column of water and spirit will be same.
Also, given water stands to a level of 12.8 cm above the mercury.
Let, h be the length of the spirit in the U- tube.
So, Pressure due to 12.8cm of water = Pressure due to h cm of spirit
or 1 x g x 12.8 = 0.8 x g x h
or h = 16 cm, is the length of the spirit in the U-tube.