ANY HELP! 2!

[Saladin]

Hey guys post any doubts on the following topics:

Physics
Chemistry
Mathematics (c1 C2 S1 FP1)
Business
and Biology, with special host nid404
For Edexcel

I will do my best to help you guys out. Please post all your problems. Will be here for another 30 min.

[Saladin]

Please post any questions that you may have on the previously stated subjects.

[mousa]

Flask X contains 1 dm3 of helium at 2 kPa pressure and flask Y contains 2 dm3 of neon at 1 kPa
pressure.
If the flasks are connected at constant temperature, what is the final pressure?
\

Thanks in advance

[slvri]

when the flasks are connected the total volume of them both is 1+2=3dm³
now using boyle's law
for flask X:p1v1=p2v2
1(2)=p2(3)
p2=0.67kPa
for flask Y:p1v1=p2v2
2(1)=p2(3)
p2=0.67kPa
total pressure=0.67+0.67=1.34kPa

[Saladin]

Thanx a lot slvri, thats the correct answer.

[mousa]

when the flasks are connected the total volume of them both is 1+2=3dm³
now using boyle's law
for flask X:p1v1=p2v2
1(2)=p2(3)
p2=0.67kPa
for flask Y:p1v1=p2v2
2(1)=p2(3)
p2=0.67kPa
total pressure=0.67+0.67=1.34kPa

Thanks a lot slvri

[Saladin]

Please post any problems that you may have with any of the subjects mentioned above.

[Saladin]

Here u go new member k..something

[vanibharutham]

Hi,

There is something that i can never seem to understand in a stress strain graph....
 the difference between the yield point and elastic limit

according to my teacher they are the same thing,

according to the edexcel book:

Yield Point = the point where a small change in stress causes a large change in strain
Elastic Limit = the point up to which a material is elastically deformed


along with that doubt, there seems to be a misconception with the definitions of the words STRENGTH and TOUGHNESS...

i did some reading, and found that toughness is the energy absorbed per unit volume, and stronger materials have a high ultimate tensile stress..

Now, once again resorting to edexcel definitions:

TOUGHNESS = the property of materials to resist plastic deformation. A large amount of force is needed to cause plastic deformation.
STRENGTH = property of materials to absorb large amounts of stress without failure...

those are a bit vague... any clarification would be great

[Saladin]

Yes, this is often something that we all get confused about:

At the elastic limit, the material does not move back to its original limit, but it still moves back a little. Like it gets deformed yes, but it still springs back, and becomes less than the extended length.

But the yield point is the point at which there is no going back. At this point the material shows plastic behavior, as the length to which u extend it remains like that, at this point slide between the molecules occur, as in the cations in the metal slide over each other and cannot go back to its original length, as the metal loses this energy as heat.

Now toughness and strength

toughness is basically the ability how much stress is required to get the material to its elastic limit, thus talking about tensile stress.
strength of a material is its ability to resist being necked, thus it is talking about compressive stress.

[nid404]

Well, You can add biology to that...I will help =)

[Saladin]

Done, changed my first post, gr8 to hav u on da team nis404!

[nid404]

Done, changed my first post, gr8 to hav u on da team nis404!

the pleasure is mine

[Saladin]

hey u guys please post any probs dat u may hav and me and nid will help u out as much as we can!

[vanibharutham]

Yes, this is often something that we all get confused about:

At the elastic limit, the material does not move back to its original limit, but it still moves back a little. Like it gets deformed yes, but it still springs back, and becomes less than the extended length.

But the yield point is the point at which there is no going back. At this point the material shows plastic behavior, as the length to which u extend it remains like that, at this point slide between the molecules occur, as in the cations in the metal slide over each other and cannot go back to its original length, as the metal loses this energy as heat.

Now toughness and strength

toughness is basically the ability how much stress is required to get the material to its elastic limit, thus talking about tensile stress.
strength of a material is its ability to resist being necked, thus it is talking about compressive stress.

Hey, thanks for that

if u let me, ill add this which i copied from this website:

Strength refers to resistance to deformation, and also to a large elastic range.

At a point called the yield point, the relationship between stress and strain depart from linear, and the material yields meaning that permanent or inelastic and plastic deformation occur.

Beyond the yield point , less stress is required for a given amount of strain (deformation). This proceeds up to the ultimate tensile strength, which is where uniform elongation is measured. At this point, a tensile specimen begins to 'neck', i.e. the change in cross-section becomes non-uniform.
Also, beyond the ultimate tensile strength, the strain increases without additional stress. If the load is not immediately removed, the material will strain to failure.

Toughness is the resistance to failure or crack propagation. It is somewhat related to strength. Very strong materials will have low toughness, i.e. low tolerance for flaws or defects, i.e. incipient cracks.

Toughness relates to the amount of energy absorbed in order to propagate a crack. Materials with high toughness require greater energy (by virtue of force or stress) to maintain crack propagation. Toughness is described in terms of a stress intensity factor (K)