Barometer reading in an elevator .

[Abhishekdas]

Barometer reading in an elevator...

Homework Statement

A barometer kept in an elevator reads 76cm when it is at rest. If the elevator goes up with increasing speed , the reading will (a).increase (b)decrease (c)remain constant (d) become zero...

Homework Equations

The Attempt at a Solution

Dont have any clue...can anyone give me a start?

 

[supratim1]

consider the change in total acceleration. if it is a upwards, then net accn = g + a

 

[Abhishekdas]

Ya i know that is the g effective you are talking about...But what to do...with that...Do i apply Bernoulli's theorem at the top of the of the mercury surface in the tube and at the surface open to atmosphere?

 

[supratim1]

just use rho(g-effective)h

 

[Abhishekdas]

Can you give me a better explanation...?

 

[bjd40@hotmail.com]

the atmos pressure is hXrhoXg(effective). the measurement is h, like "the pressure is 76cm". now if g effective is greater than g actual, h would have a less value for same pressure, and vice-versa.

 

[Abhishekdas]

Hi bjd40@hotmail.com...
So you mean to say that the pressure at the surface of mercury in beaker is same (equal to atmospheric pressure which is constant close to the earth)...SInce it is also = h*rho*geff as geff has become 'g+a' ie increased the 'h' has to decrease...Is that it?