Question 5
Find the pressure produced by a mercury column 50 cm high. (density of mercury = 13 600 kg m−3; g = 10 m s−2)
The right answer is the one marked above.
68 000 Pa. First convert: 50 cm = 0.5 m. Then P = 0.5 × 13 600 × 10 = 68 000 Pa.
680 000 Pa comes from turning 50 cm into 5 m by mistake, and 136 000 Pa from taking the height as 1 m. Always convert the height to metres before substituting.