Atmospheric Pressure and Mercury in a Test Tube

AI Thread Summary
The discussion revolves around understanding the behavior of mercury in a test tube under different atmospheric pressure scenarios. Participants suggest using a free body diagram (FBD) to analyze the forces acting on the mercury blob in each situation. The original poster seeks clarification on the specific lengths of mercury in two situations, questioning how atmospheric pressure influences these lengths. There is a consensus that atmospheric pressure plays a crucial role in holding the mercury in place, despite it being stationary in all cases. The need for a clearer understanding of the forces at play and their effects on mercury's position is emphasized.
yenhan10
Messages
3
Reaction score
0
The problem statement



Recently I came across this problem and couldn't understand it.

I know that in situation 1, the length of the specific place will be decreased; In situation 2, it will be increased.

Can someone help me here? Thanks first!
 
Last edited by a moderator:
Physics news on Phys.org
yenhan10 said:
The problem statement



Recently I came across this problem and couldn't understand it.

I know that in situation 1, the length of the specific place will be decreased; In situation 2, it will be increased.

Can someone help me here? Thanks first!

Welcome to the PF.

With problems like this, you need to draw a free body diagram (FBD). For each situation, draw the forces that are acting on the mercury blob.
 
Last edited by a moderator:
What holds the mercury in the specified locations in all the cases? Why the difference?
 
berkeman said:
Welcome to the PF.

With problems like this, you need to draw a free body diagram (FBD). For each situation, draw the forces that are acting on the mercury blob.

Hi do you mean this?


I need to know exactly what are the lengths for both specific situation...
 
Last edited by a moderator:
voko said:
What holds the mercury in the specified locations in all the cases? Why the difference?

Hi I'm not sure. I was given this problem in a practice. Maybe assuming there's an unknown gas inside? Situation 2 might be held by the atmospheric pressure? I have to find out the exact length covered by mercury.. Help!
 
Observe that in situations 1, 2 and 3, in the first picture, atmospheric pressure is always present on the open end of the tube, and pushes the mercury inward. What is its force?

But the mercury is stationary in all the cases. Why?
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

What does atmospheric pressure have to do with the gauge pressure?
Replies
3
Views
1K
Atmospheric pressure and water pressure - Boyle's law
Replies
6
Views
791
Pressure in a gas container measured with a barometer and a U pipe
Replies
6
Views
2K
Gas in mercury manometer, finding its normal volume
Replies
2
Views
1K
Conceptual Issue Dealing With Atmospheric Pressure
Replies
4
Views
2K
Mercury barometer with a small amount of air
Replies
7
Views
2K
Calculating Work Done by Gas in a Mercury-Filled U-Tube with Right Angle Bends"
Replies
10
Views
2K
Mercury Barometer Experiment: Atmospheric Pressure
Replies
1
Views
2K
A water-bottle demonstration of atmospheric pressure
Replies
6
Views
2K
Determine the change in elevation of mercury in this manometer
Replies
17
Views
3K

Hot Threads

Recent Insights

Back
Top