A barometer kept in an elevator accelerating upward reads 76cm. T… - Vidyadip

MCQ

A barometer kept in an elevator accelerating upward reads 76cm. The air pressure in the elevator is

A
76cm.
B
< 76cm.
✓
> 76cm.
D
zero.

✓

Answer

Correct option: C.

> 76cm.

When the elevator is going upwards with acceleration a, the effective acceleration is a' = (g + a).
Thus, pressure is given by:
$\text{P}=\text{h}\rho(\text{g}+\text{a})$
Air pressure in the elevator $=\text{p}=\text{h}'\rho\text{g}$
Because the pressure is the same, h' > h.
$\therefore$ Air pressure > 76cm.

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