A uniform capillary tube, closed at one end, contained air trapped by a thread of mercury 85mm long. when the tube was held horizontally, the length of the air column was 50mm. when it was held vertically with the closed end downwards, the length was 45mm. find the atm in N/m²
(take g=10, density of mercury = 14 000kg/m³)
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Answer:
Let atm = P1
Volume of air trapped is proportional to length of air column
When it is horizontal, only atm is involved
when it is vertical, pressure of air in the capillary tube = atm + pressure due to mercury column
= P1 + 14000 * 10 * 0.085 (pgh)
= P1 + 11900
Hence, using P1V1 = P2V2 (Boyle's Law)
P1 (50) = (P1 + 11900) (45)
Solving the equation,
P1 = 107000 Pa (3 sf)
