A liquid $X$ of density $3.36\  g/cm^3$ is poured in a $U-$ tube, which contains $Hg$. Another liquid $Y$ is poured in left arm with height $8\  cm$, upper levels of $X$ and $Y$ are same. What is density of $Y$ .......... $g/cc$

A barometer kept in a stationary elevator reads $76 cm$. If the elevator starts accelerating up the reading will be

Mention two instruments which measure the atmospheric pressure.

An open-ended U-tube of uniform cross-sectional area contains water (density $10^3 kg m ^{-3}$ ). Initially the water level stands at $0.29 m$ from the bottom in each arm. Kerosene oil (a water-immiscible liquid) of density $800 kg m ^{-3}$ is added to the left arm until its length is $0.1 m$, as shown in the schematic figure below. The ratio $\left(\frac{h_1}{h_2}\right)$ of the heights of the liquid in the two arms is-

Radius of an air bubble at the bottom of the lake is $r$  and it becomes $ 2r $ when the air bubbles rises to the top surface of the lake. If $P $ $cm$  of water be the atmospheric pressure, then the depth of the lake is

A $U$ -tube of small and uniform cross section contains water of total length $4H$. The height difference between the water columns on the left and on the right is $H$ when the valve $K$ is closed. The valve is suddenly open, and water is flowing from left to right. Ignore friction. The speed of water when the heights of the left and the right water columns are the same, is :-