'O' level physics: pressure

• donkhead333

  3 Oct 09, 22:37

  

  As above.

  Don't really understand the force vectors involved, would be great if someone could enlighten me

  P.S. sorry for the crappy drawing, was the best I could do with my mediocre "painting" skills

• yiha093

  4 Oct 09, 01:39

  this 1 TYS 1 right. i got do.

  1st tube . trapped air =  atm . cause mercury force is downwards.

  2nd tube trapped air+ mercury= atm

  do sim. eqn .

  ta-da.

• donkhead333

  4 Oct 09, 08:27

  But how do you calculate the pressure of the trapped air?

  Wouldn't the pressure of the trapped air + pressure of the mercury be lesser than that of the atm pressure?

  Do you get the pressure of the trapped air from the first diagram?

  Like: 101000/0.42 to find pressure per metre?

  And then use the answer for the next diagram?

  But then again..the pressure of the air pocket in the second diagram should be lesser because the same number of air molecules occupy a larger space..

  >.<

• yiha093

  4 Oct 09, 13:51

  u need to form 2 eqn from 1st and 2nd tube and solve

  sim. eqn.  u know? ?   -.-

  do some logical thinking to deduce the equations.

  and no .  trapped air+ mercury= atm . 

  no u canot find the pressure from 1st diagram. use sim. eqn.

  the diagram isnt drawn 2 scale.

• qdtimes2

  4 Oct 09, 17:14

   can show the workings? i dun understand also