MCQ
A barometer kept in an elevator accelerating upward reads 76cm. The air pressure in the elevator is
- A76cm.
- B< 76cm.
- ✓> 76cm.
- Dzero.
✓
Answer
Correct option: C.
> 76cm.
Explanation:
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.
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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