Question 4
What happens to the mercury column if the tube of a mercury barometer is tilted?
The right answer is the one marked above.
Its vertical height stays at 76 cm. The mercury appears to climb further along the tube, but measured vertically the height is unchanged.
The reason is property (iv) of liquid pressure — it depends on the vertical height of the column alone, not on its length or its tilt. The same holds if the tube is sunk a little deeper; only the height of the vacuum changes.