# A barometer kept in an elevator reads 76cm when it is at rest. If the elevator goes up with

Q: A barometer kept in an elevator reads 76 cm when it is at rest. If the elevator goes up with increasing speed, the reading will be
(a) zero

(b) 76 cm

(c) < 76 cm

(d) > 76 cm

Ans: (c)

Sol: As atmospheric Pressure is same in both the condition

$\displaystyle \rho g h = \rho (g + a)h’$

$\displaystyle h ‘ = \frac{g }{g + a} h$

Hence , h’ < 76 cm