ALL PHYSICS DOUBTS - POST HERE !!

[pglasg74]

look at the temperature difference .. only A has a temperature rise of 2 *C .. greatest thermal capacity


others have increased by  8, 4,6 as their thermal capacity is lesser

vin can u explain.. i dont understand questions like #20 in summer 07.. like i dont get it, isnt wavelength supposed to decrease when they enter deeper, why are they further apart? why is the answer c not b :S:S:S:S


and i posted the fuse question before..

[Syed Kazim]

Please please can someone answer these questions:  S06 - Qs 19 and 20.

Question 19: D.

It cannot be A because radiation is not prevented by an air gap.
It cannot be B because heat does pass through the sides of the cup.
It cannot be C because hot air rises and thus it will not go by convection to the bottom.
It has to be D.

[High-R]

lol hamz no 1 noes
acha sun konsa ppr kr rahi hai!!!

@6394 lol ya ...finishd all ppr..no more i think ill do

PPL PLZ TELL ME....VIN???

[Syed Kazim]

Question 19: D.

It cannot be A because radiation is not prevented by an air gap.
It cannot be B because heat does pass through the sides of the cup.
It cannot be C because hot air rises and thus it will not go by convection to the bottom.
It has to be D.

Question 20: D.

It cannot be A because that is the definition of wave-length.
It cannot  be B because that is half a wave-length.
It cannot be C because speed of a water wave is not measured by particles moving up and down rather by wave-front moving along a surface.
It has to be D.

[Vin]

vin ill give u the fuse qn.. here:

"A mains current can safely supply a current of 40 A. A hairdryer takes 2A. It is connected to the circuit by a lead which can safely carry up to 5 A.
Which fuse is best to use in the plug fitted to the hairdryer lead?"

1 A, 3 A, 50 A OR 10 A?

ok i think its 3A ..   50 A and 10 A are out of the ques because they will cause the wire to melt as it can carry only 5 A
1 A is used then the dryer will not work because it requires a minimum of 2 A

[Ivo]

vin can u explain.. i dont understand questions like #20 in summer 07.. like i dont get it, isnt wavelength supposed to decrease when they enter deeper, why are they further apart? why is the answer c not b :S:S:S:S


and i posted the fuse question before..

If you look at the question, it says from shallow to deeper water, so they travel quickly don't they, the waves when they enter the deeper water.

Must be C because, lambda=v/f so if speed increases, frequency is constant (same colour), so wavelength increases, so lines are further apart.

Got it?

[High-R]

hey ppl wats gravitational ENERGY?
i got this question of the stone being thrown upwards and comes down.....and it asks where is the gravitational energy the least....so the answer is: tht the gravitationalenergy is least when the stone is just about to touch the ground!!!

can anyone explain y?...and how..wats this Gr.Energy?

plz reply!!!...HURRY!!!!!!!!!

[pglasg74]

If you look at the question, it says from shallow to deeper water, so they travel quickly don't they, the waves when they enter the deeper water.

Must be C because, lambda=v/f so if speed increases, frequency is constant (same colour), so wavelength increases, so lines are further apart.

Got it?

no the answer says which diagram shows the waves in the DEEPER region..

[pglasg74]

In Beta decay a neutron changes to a proton and an electron. The proton remains in the nucleus and the electron is emitted as a beta-particle. The new nucleus has the same nucleon number, but its proton number increases by one since it has one more proton.

thanks, now can u answer "A mains current can safely supply a current of 40 A. A hairdryer takes 2A. It is connected to the circuit by a lead which can safely carry up to 5 A.
Which fuse is best to use in the plug fitted to the hairdryer lead?"

1 A, 3 A, 50 A OR 10 A?


and pls explain how to select the best fuse..

[Ivo]

plz reply!!!...HURRY!!!!!!!!!

GPE: energy due to position.

KE: energy due to motion.

So at start, GPE is greatest (no motion).  When thrown up (GPE converted to KE) then momentarily stops at top of flightpath (GPE again) then when it drops (GPE to KE increases), so just before it hits, KE is greatest, therefore a lot of GPE has been converted, therefore GPE is least.  Got it?

[Vin]

OK GUYS IMMA SLEEP NOW !!   Its 4 am here !!.. n i need some sleep ..sorry guys if u r questions are pending  

BEST OF LUCK TO ALL !!

[Ivo]

no the answer says which diagram shows the waves in the DEEPER region..

Excactly, the words in the question say they travel quickly in deeper water, so speed of waves are quicker, wavelength increases, as explained with the formula before.

[pglasg74]

ok i think its 3A ..   50 A and 10 A are out of the ques because they will cause the wire to melt as it can carry only 5 A
1 A is used then the dryer will not work because it requires a minimum of 2 A

yeah i got that.. how about this one?

The current in a lamp at full brightness is 0.25 A. The flexible cable to the lamp is designed for currents upto 5 A so it can safely carry teh 0.25 taken by the lamp. Which fuse should be inserted in the plug at the other end of the cable?

.. teh answer is 1

[Syed Kazim]

vin can u explain.. i dont understand questions like #20 in summer 07.. like i dont get it, isnt wavelength supposed to decrease when they enter deeper, why are they further apart? why is the answer c not b :S:S:S:S


and i posted the fuse question before..

Water waves have a shorter wave-length in shallow water, i.e. they travel more slowly.
Water waves have a longer wave-length in deep water, i.e. they travel fast.

[Ivo]

thanks, now can u answer "A mains current can safely supply a current of 40 A. A hairdryer takes 2A. It is connected to the circuit by a lead which can safely carry up to 5 A.
Which fuse is best to use in the plug fitted to the hairdryer lead?"

1 A, 3 A, 50 A OR 10 A?


and pls explain how to select the best fuse..

3A, cos hairdryer only needs 2A.  In general, take the max current needed by appliance, then select the fuse with rating of the next one up.  So 4A, would need 5A fuse, for example.  Using 13A fuse for this would be dangerous, cos of the larger current.