# Physics, Chemistry and Biology: Post your doubts here!

#### semsemhosam

Assalam-o-Alaikum.
Post your Physics, Chemistry and Biology doubts in here and members, along with me will try their best to help you out.

#### Astellaz

Physics Problem...
A uniform metal tube of length 5m and mass 9kg is suspended horizontally by two vertical wires attached at 50 cm and 150 cm respectively from the ends of the tube. Find the tension in each wire.
Hope you can help ^-^

#### Anon

total force downwards = 90N

let tension in one wire to be 'p'
and other 'q'

distance of p from the center = 100
distance of q =200

ratio is 1:2

as the support the total wieght of 90 N.
combine tension of the wires will be 90N.

q will have a greater moment being further away, so I think it is:

p=30N
q=60N

#### Anon

A mistake:
q will have lower tension I think..

it would be:

p= 60N
q= 30N

Moment = l x force.

If length is more, the force would be less

#### Astellaz

total force downwards = 90N

let tension in one wire to be 'p'
and other 'q'

distance of p from the center = 100
distance of q =200

ratio is 1:2

as the support the total wieght of 90 N.
combine tension of the wires will be 90N.

q will have a greater moment being further away, so I think it is:

p=30N
q=60N

Hi again Anon.....Ive been seein u around lately....
Now cn u also solve this problem for me pls????? ^-^
A uniform metre ruleof weight 0.9N is suspended horizontally by 2 vertical loops of thread A and B placed at 20cm and 30cm from its ends respectively. Find the distances from the centre of the rule at which a 2N weight must be suspended:
i) to make loop A become slack
ii) to make loop B become slack

#### Astellaz

Sorry forgot to thnk you for answering...so thnx ^-^

#### *MK*skydiver :D

is Antimony a metalloid ? I've looked it up in many places i got different answers but most of the websites said its a metalloid ....my teacher doesnt agree ....so is it or is it not ? thanks

#### Iridescent

it is a metalloid i guess.

#### John 1234

A very simple question from me... What is the difference between evaporation and crystallisation... What does one method offer that the other does not? I'm posing this question because both methods of separation seem to satisfy the same objective: extracting a dissolved substance from a solution...

#### semsemhosam

is Antimony a metalloid ? I've looked it up in many places i got different answers but most of the websites said its a metalloid ....my teacher doesnt agree ....so is it or is it not ? thanks
metalloid

#### sea_princess

A very simple question from me... What is the difference between evaporation and crystallisation... What does one method offer that the other does not? I'm posing this question because both methods of separation seem to satisfy the same objective: extracting a dissolved substance from a solution...
in crystallisation you heat the solution then cool it down quickly ,this makes the molecules of the salt bind some water molecules around them forming crystals
in evaporation ,u remove all the water , so the salt is like a powder .also if you heated a crystallised salt ,you'll remove the water of crystallisation and it turns to powder.
yes, both are ways of extracting substances from solutions ,but evaporation can be done when the substance don't dissolve in the solution ,but for crystallisation to occur the substance has to dissolve in the solvent

#### MuslimGirl

in crystallisation you heat the solution then cool it down quickly ,this makes the molecules of the salt bind some water molecules around them forming crystals
in evaporation ,u remove all the water , so the salt is like a powder .also if you heated a crystallised salt ,you'll remove the water of crystallisation and it turns to powder.
yes, both are ways of extracting substances from solutions ,but evaporation can be done when the substance don't dissolve in the solution ,but for crystallisation to occur the substance has to dissolve in the solvent
yes u r right.

#### Astellaz

Pls help me solve this question
I know its rather hard but just tell me what you think is right please...
A uniform metre rule of weight 0.9N is suspended horizontally by 2 vertical loops of thread A and B placed at 20cm and 30cm from its ends respectively. Find the distances from the centre of the rule at which a 2N weight must be suspended:
i) to make loop A become slack
ii) to make loop B become slack

#### Parfals

sure will giv u the answer

#### Iridescent

Chemistry:
Q: Suggest a reson 4 only 'roughly' twice as much hydrogen gas being produced at the cathode as oxygen gass at the anode in the electrolysis of water.
Q: During da electrolysis of molten aluminium chloride (AlCl3) the carbon anodes r burned away. Explain why dis shud hapen n write a balanced chemical equation 4 da reactions dat take place.
Thanx!

#### GetSomeLife

Chemistry:
Q: Suggest a reson 4 only 'roughly' twice as much hydrogen gas being produced at the cathode as oxygen gass at the anode in the electrolysis of water.
Q: During da electrolysis of molten aluminium chloride (AlCl3) the carbon anodes r burned away. Explain why dis shud hapen n write a balanced chemical equation 4 da reactions dat take place.
Thanx!

Q1: H+ ions are attracted to d cathode while OH- ions are attracted to the anode. All the hydrogen is released at the cathode but sum of the OH- ions r used to form water along wid the O2! Therefore, almost double de amount of H2 iz produced dan d amount of O2!
u can see dis frm da eqn:
Cathode:
2H+ + 2e- gives H2
Anode:
4OH- gives 2H2O +O2 + 4e-

Q2: i thinku mistook Aluminium OXIDE for CHLORIDE! cuz den o2 iz released at such a high temperature the carbon anode reacts with the oxygen to form CO2 and escape as gas......thrfor they hav to be replace frequently!

#### Iridescent

No it is aluminium chloride in the book.
aluminium oxide (bauxite) is used in the manufacture of Al bt dis is diferent!

#### GetSomeLife

No it is aluminium chloride in the book.
aluminium oxide (bauxite) is used in the manufacture of Al bt dis is diferent!

wel, if dats da case den the the chlorine produced reacts wid da carbon to form carbon tetrachloride:

C + 2Cl2 gives CCl4 ....which is a gas due to high temp!

#### Iridescent

wel, if dats da case den the the chlorine produced reacts wid da carbon to form carbon tetrachloride:

C + 2Cl2 gives CCl4 ....which is a gas due to high temp!
Thanx!

#### tania

I am having problem with moments. Especially stable,neutral and unstable equilibrium..plx help!!!!!!!!!!