Why is there vacuum above the level of mercury in a mercury barometer?

answer: a mercury barometer works by stabilizing the level of mercury in the sealed glass tube with the atmospheric pressure on the open mercury chamber.

as a general rule, scissors have blades less than 6 in (15 cm) long and usually have handles with finger holes of the same size. shears have blades scissors used to cut hair or fabric must be much sharper

a skateboard rolling across the street - apex