Question

Water barometer is possible provided barometer tube is 9 m long,​

Answer 1

So, to measure the atmospheric pressure, which is 760mm of mercury you need a barometer ,with mercury, of length slightly more than 0. ... If you use water, you have to have the length of barometer of length (or height) 13. 534 times the length of mercury barometer, which may be more than 11m in length.

I hope this answer will help you dear....