Question

A barometer kept in an elevator accelerating upward reads 76 cm. The air pressure in the elevator is
(a) 76 cm
(b) < 76 cm
(c) > 76 cm
(d) zero

Answer 1

(c) > 76 cm

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