Question

A mercury barometer reads $75cm$ in a stationary lift. What reading does it show when the lift is moving downwards, with an acceleration of $1m/s^2$?

Answer 1

Here we have to use Pseudo force connect,

acceleration , $a=1m/s²$ is downward so, net acceleration is , $a_n=(g-a)$ downward.

now formula will be ,

$\rho g{h}^{\prime }=\rho (g-a)h$

Here, h' is final height of barometer ,

⇒ $h^{\prime }=h(1-a/g)$

Now, put $a=1m/s²,g=10m/s²,h=75cm$

$h^{\prime }=75(1-1/10)=75\times 9/10=67.5cm$

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