Signup
LoginPhysics - Pressure
14 posts
-
-
In that post Darkness_hacker99 mentioned, eagle posted the solution as this:
at surface:
pressure, P1 = 1atm (atmospheric pressure equivalent to 10m of water), V1 = 6cm3at bottom of lake:
pressure, P2 = 3 atm (atmospheric pressure + 20m of water), V2 = unknownUsing Bolye's Law, P1V1 = P2V2
V2 = 2cm3
But the thing is, I haven't learnt about this Boyle's Law thing. Nor have I heard of it. My brother tried to teach me using this method but he told me not to attempt this question since I havent been taught about the law before. why is P1 = 1 atm and P2 = 3 atm?
-
-
-
Originally posted by eagle:
the equation means this
original volume multiplied by original pressure equals to final volume multiplied by final pressure
or vice versa
Do you understand the above part first? Understand then we proceed to the next step
So how do you get 1 atm and 3atm? I don't understand this because I havent learnt this before. But I am interested to find out.
-
-
-
Oh yea and there's this question from the Ten Years series.
2 cubes are made form the same material. one cube has sides that are twice as long as the other. standing on one face, the small cube exerts a pressure p = w/a, where a is the area of the face. what is the pressure exerted by the larger cube standing on ONE of its faces?
I got this answer as 4p but the answer booklet writes 2p. can anyone explain?
-
-
-
Originally posted by bonkysleuth:
So how do you get 1 atm and 3atm? I don't understand this because I havent learnt this before. But I am interested to find out.1 atm is pressure at the water surface. That's because it is the air pressure.
and at depth of 20m, the total pressure comes from 1atm (at water surface) + 20m of water. Since 10m of water = 1atm, that means total pressure = 3atm
-
-
-
Originally posted by bonkysleuth:
Oh yea and there's this question from the Ten Years series.
2 cubes are made form the same material. one cube has sides that are twice as long as the other. standing on one face, the small cube exerts a pressure p = w/a, where a is the area of the face. what is the pressure exerted by the larger cube standing on ONE of its faces?
I got this answer as 4p but the answer booklet writes 2p. can anyone explain?
if the small cube has face area a, the large cube has area 4a.
Also, if the small cube has weight w, the large cube has weight 8w, since weight is proportional to volume (same material means same density).
Thus, pressure exerted by larger cube = 8w / 4a = 2 w/a = 2p
-
-
-
Originally posted by eagle:
if the small cube has face area a, the large cube has area 4a.
Also, if the small cube has weight w, the large cube has weight 8w, since weight is proportional to volume (same material means same density).
Thus, pressure exerted by larger cube = 8w / 4a = 2 w/a = 2p
Thanks. But I somehow dont get this part:if the small cube has weight w, the large cube has weight 8w, since weight is proportional to volume (same material means same density).
Thus, pressure exerted by larger cube = 8w / 4a = 2 w/a = 2p
i still dont know why weight is proportional to volume. havent heard of that before.
-
-
-
Originally posted by bonkysleuth:
Thanks. But I somehow dont get this part:if the small cube has weight w, the large cube has weight 8w, since weight is proportional to volume (same material means same density).
Thus, pressure exerted by larger cube = 8w / 4a = 2 w/a = 2p
i still dont know why weight is proportional to volume. havent heard of that before.
Ok.
One of the ways to see it is:
Weight is proportional to mass.
Mass is proportional to volume (since mass = density * volume)Therefore, Weight is proportional to volume.
-
tat being e case, is history in e making