Answer :
Final answer:
As the elevator accelerates upwards, the atmospheric pressure decreases due to the reduced weight of the air above the barometer, causing the barometer reading to drop below 76 cm. The correct answer is (d) < 76 cm
Explanation:
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? The correct answer is (d) < 76 cm. This is because as the elevator accelerates upwards, the pressure exerted by the air inside it decreases due to a reduction in the weight of the air above the barometer. A barometer measures atmospheric pressure, which is directly related to the weight of the air column above it. In an accelerating upward elevator, the effective weight of the air decreases, leading to a lower atmospheric pressure reading. The greater the acceleration, the more significant the decrease in the barometer reading, similar to the principle that a scale reading increases with greater acceleration due to the force needed to accelerate an object upwards.
