MCQ
A barometer kept in an elevator reads $76 \,cm$ when the elevator is accelerating upwards. The most likely pressure inside the elevator (in $cm$ of $Hg$ ) is ........
- A$74$
- B$75$
- C$76$
- ✓$77$
✓
Answer
Correct option: D.
$77$
d
(d)
(d)
When the elevator is going upwards with acceleration a then net acceleration will be the sum of a and $g($ acceleration due to gravity). $= g + a$
$\therefore$ Pressure $= h \rho( g + a ) dyne / cm ^2$
$=\frac{76 \times 13.6 \times( g + a )}{76 \times 13.6 \times g } cm \text { of } Hg .$
$=1+\frac{ a }{ g } > 1 cm \text { of Hg. }$
final pressure should be more than $76\,cm$ of $hg$
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