Q1: 
why there is pressure difference beween accume and air 
rohan raj 
3/5/2014 
Ans: 



Q2: 
what is the relation between pressure and teprature? 
anish 
16/2/2010 
Ans: 



Q3: 
what is force? 
abigail 
5/11/2009 
Ans: 



Q4: 
what is the relation between pressure, temp, viscosity, discharge and velocity for fluids? im really confused please help! 
ratheesh 
11/9/2009 
Ans: 



Q5: 
why moon moves around earth but it does not moves around the sun 
amar 
19/2/2009 
Ans: 



Q6: 
why velocity increases / decrease with drop/rise in pressure? you didn't answer first one in 48 hours. that's why i am again asking 
yogesh mehndiratta 
22/12/2008 
Ans: 



Q7: 
when area decreases pressure decreases & velocity increases. why velocity increases & vice versa decreases. 
yogesh mehndiratta 
20/12/2008 
Ans: 



Q8: 
why dose there need to be changes in some cooking recipes for cooking and baking at high elevations 
kristinn 
25/9/2008 
Ans: 



Q9: 
How to convert the pressure drop say 100 mm of Hg to flow rate? 
skarp 
25/8/2008 
Ans: 



Q10: 
Kindly delete the below question.I find out the answer.For constant DP ,whatever may be the pressure variation,Mass flow rate constant 
skarp 
28/4/2008 
Ans: 



Q11: 
In a pipe, one side is 3.2bar and other side is 2 bar, differential pressure is 3.22=1.2bar.The massflow rate is 400lpm.If the pressure on two side of the pi varies but Differential pressure is same (2.21=1.2bar) whether mass flow rate will be same 
skarp 
22/4/2008 
Ans: 



Q12: 
Why can't we feel pressure due to the atmoshere? 
Karen 
13/3/2008 
Ans: 
We don't feel the pressure of the atmosphere because the pressure within our bodies counterbalances the pressure of the gas in the atmosphere. This is because the air spaces inside our bodies are at much the same pressure as the air outside. The puncture of a space suit in the vacuum of outer space immediately leads to the rupture of the body because there is nothing outside to balance the body's inner pressure. 


Q13: 
i know alot now about pressure but still one confusion is in my mind. whether the pressure velocity are directly propotional to each other or inversely propotional to each other? kindly answer. 
TalhaAwan 
25/12/2007 
Ans: 
They are inversely proportional, as per "Bernoulli effect", an increase in the flow velocity causes a lowering of the fluid pressure and vice versa. 


Q14: 
relation ship between temperature and vaccume means negetive pressure 
mukesh 
2/12/2007 
Ans: 
Actually no, there is nothing like a negative pressure, a vacuum pressure will keep on reducing to values 10(4) or 10(6) torr but it will not go negative. The relationship of proportionality exists between temperature and pressure in vacuum, as one increases so does the other. So as such negative pressure as a concept does not exist. 


Q15: 
Do you have trial version? 
ATHK 
15/11/2007 
Ans: 
No we do not have any trial version as yet, actually you can see a preview of the animtion, which in most cases gives a fair idea of what the animation contains 


Q16: 
What is the relation between flash and fire point of bitumen and atmospheric pressure? 
ammar hassis 
5/10/2007 
Ans: 
Vapor production at a given temperature is opposed by atmospheric pressure. A flammable liquid can form an ignitable mixture only if sufficient concentration of vapor is present in air. If the concentration increases, then vapor pressure increases. Boiling or vapor production occurs at a lower temperature if atmospheric pressure is reduced. Therefore, flash/ fire point decreases as atmospheric pressure decreases. Flash point decreases linearly by 1deg F for every 800 ft increase in altitude. 


Q17: 
A closed container consists of air molecules.The temperature of the container is increased.viscosity will also gets increased.what happens to pressure it will increase or decrease ? 
skarp 
26/9/2007 
Ans: 
Actually the viscosity decrease with temperature increase but for a gas it actually it does not matter at molecular level. Pressure is determined by collisions of molecules with the walls. The molecules of air will start moving faster as increase in temperature is proportional to KE, the collisions between the walls of the container and molecules and among molecules will be more vigorous due to higher KE, this will lead to higher pressure. Thus upon heating the pressure will increase. 


Q18: 
When heat is applied to the hollow cylinder ,the outer portion expanded and what will happen to inner portion of cylinder ? 
skarp 
18/9/2007 
Ans: 
Take a solid cylinder; heat it, you will see it expands (not contracts) on heating. Now cut an inner cylinder from it to get a hollow cylinder, place the cut cylinder inside it again and heat them both, both will expand and at the same rate as if they were one solid cylinder. The outer cylinder did not expand inwards. Why? Because heating increases distance between atoms, contraction will bring atoms closer, that will violate the law. For a disc or cylinder on heating hole will become bigger. 


Q19: 
what is the reynolds no for the pipeflow 
maruti 
10/9/2007 
Ans: 
The Reynolds (Re ) is a nondimensional parameter used to estimate the relation between inertia and viscous forces. It is used to find if a fluid flow is laminar, transition (where the flow is neither fully laminar nor fully turbulent) or turbulent. It is a function of fluid speed is V; the orifice diameter is d, density (rho) or absolute dynamic viscosity (mu). If Re>2320, turbulent flow will occur, and if viscous forces are big enough in compare to inertia, Re<2320, laminar flow will occur. 


Q20: 
what will happen if vacuum is applied to pressure cooker 
parag vandkar 
10/9/2007 
Ans: 
A pressure cooker operates due to vapor pressure i.e. pressure of the molecules that have evaporated from the liquid counteracting further evaporation, if a vacuum is created inside a cooker it will have no effect as molecules will evaporate at lower temperature to fill up the vacuum, once the vacuum is filled up then vapor pressure will come into play again. 


Q21: 
Does the pressure changes cause any influence on the gravitation?is there any relation between them? 
stanley raj 
2/8/2007 
Ans: 
Air Pressure or more correctly atmospheric pressure is a resultant of gravity pull on molecules of air, causing them to cluster nearer to earth, there are more molecules at the bottom than at the top of air column causing a pressure on everything below but this does not affect gravity at all, gravity's magnitude is much more than the pressure effect of atmosphere. 


Q22: 
what is the difference between pressure and stress both have same units.consider 10N force and 5mm2 area .pls tell me the difference 
skarp 
3/7/2007 
Ans: 
In SI units both are expressed in Pascal (Pa) or N/m2 or m1·kg·s2 and they share a cause effect relationship. Pressure causes stress. Pressure is scalar while stress is a vector. For a solid body, Pressure is the force per unit area applied on a surface in a direction perpendicular to that surface while stress is the tensile and compressive stresses in solid objects, it is the internal force per area that balances and reacts to external pressure, these terms are often used interchangeably. 


Q23: 
air pressure inside a pressure cooker 
Maheen 
17/3/2007 
Ans: 
Standard is 15 psi, the range can vary from 5 15 psi (5 psi is rarely used sometimes for delicate food like fish or shrimp , 910 psi is sometimes used for rice dishes, or puddings) 


Q24: 
Can u tell me , What are the assumption of Bernoulli s Theorem for compressible and incompressible fluid ? 
skarp 
31/1/2007 
Ans: 
For both conservation of mass and energy is assumed. For incompressible fluids, we ignore viscosity, compressibility, and rotational and thermal effects here incompressible flow means that density is constant along a streamline. This gives an equation P/rho + ½ v^2 + gh=constant. For a compressible flow there is a change in density along a fluid flow and is accounted for by adding a specific internal energy constant to P/rho (Errata  18/1/2007, by mistake written ideal fluid to be compressible) 


Q25: 
pressure=force/area,pressure is inversely proportional to area.so pressure should increase when area decrease. consider a tapper pipe 10cm on one side and 5cm on the other.according to bernoulli s theorem the pressure decreaseswhen area decrease? how 
skarp 
29/1/2007 
Ans: 
Pressure is the weight of molecules of fluid acting upon a horizontal pipe crosssection area. Taking 10 cm long pipe, the pressure at 10 cm end is caused by the larger number of molecules. Inside at 5 cm crosssection, “lesser” number of molecules are present so lesser force & pressure. Now make the pipe vertical then at narrow opening, higher pressure will result as “full” weight acts on a lesser area. In case of horizontal pipe, the whole weight was not acting on a cross section. 


Q26: 
THANKS GOT IT....REALLY GREAT!!!!!!!!!!! 
skarp 
23/1/2007 
Ans: 
You are welcome, it was enjoyable for us too. Thanks 


Q27: 
Thats great but at the end P(a)+1/2 rho v(a)^2=P(b)+1/2 rho v(b)^2 by this eqn .how do u say that pressure is inversely proportional.i am not able to understand .pls clear my doubt by that eqn 
skarp 
23/1/2007 
Ans: 
I think you are imagining a=k/b type relationship but remember a = kb is also inverse proportionality, if b increases, a is more negative hence reduces. In Bernoulli’s eq. as energy is constant hence either side of the equation is constant or generalizing it P + K v^2 = constant, where K = 1/2 rho ( rho’s value remains same for the incompressible fluid), the eq. can be P + K v^2 = M. This changes into P = M  K v^2. If v increases, P will have a greater negative value or reduce. Get it? 


Q28: 
how pressure drop with increase in velocity according to bernoulli.Any equation that pressure is inversely proportional to velocity.pressure= force/area so pressure is inversely proportional to area.In venturi area decreases so pressure should increa 
skarp 
19/1/2007 
Ans: 
A fluid has additional energy due to pressure of molecules besides KE and PE. In a tapering fluid tube if we take two cross sections near ends, the static pressure P in energy terms is P=F/A=(Fd)/(Ad)=Work/Vol=E/Vol, total energy at two cross sections is P(a)V+1/2m v(a)^2+mgh(a)=P(b)V+1/2 m v(b)^2+mgh(b), divide by volume to get P(a)+ ½ rho v(a)^2+rho gh(a)=P(b)+1/2 rho v(b)^2+ rho gh(b), neglect gravity we get P(a)+1/2 rho v(a)^2=P(b)+1/2 rho v(b)^2. If v(b) increases P(b) has to reduce. 


Q29: 
what is the relation between pressure and velocity. 
skarp 
18/1/2007 
Ans: 
Relationship between pressure and velocity of a fluid is governed by Bernoulli’s principle, it implies that the pressure falls where the fluid flows faster and visaversa. An ideal fluid (a nonturbulent, compressible and barotropic fluid undergoing steady motion example low speed air) with no external work being performed on the fluid, an increase in velocity occurs simultaneously with decrease in pressure or gravitational energy. Application is in aircraft lift, Venturi tubes and carburetors. 


Q30: 
Does the pressure cooker produce the same boiling point temperature at sea level as it does at higher elevations? 
Brian Washburn 
17/4/2006 
Ans: 
Yes, the same, cooker is an enclosed system and is unaffected by outside pressure whether below or above sea level. The need to cook longer at higher altitudes using pressure cooker occurs, because it is colder than at sea level hence more heat is required, also the relief valve is under lesser pressure from outside and releases earlier than at sea level causing loss of heat and pressure. 

