Question

A mercury barometer reads 75 cm in a stationary lift. What reading does it show when the lift is moving downwards, with an acceleration of 1 m/s²?

Answer 1

Here we have to use Pseudo force connect, 

acceleration , a = 1 m/s² is downward so, net acceleration is, 

a_n​ = (g−a) downward. 

Now formula will be, 

ρgh′ = ρ(g−a)h 

Here, h' is final height of barometer,

⇒ h′ = h(1−a/g)

Now, put a = 1 m/s², g = 10 m/s², h = 75 cm

h′ = 75(1 − 1/10) = 75 × 9/10 = 67.5 cm 

Hence, 67.5 cm is the reading does it show when the lift is moving downward, with acceleration of 1 m/s².