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Biology; Chemistry; Physics: Post your doubts here!

bubbles1997

bubbles1997

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Aoa. Help me what is amplitude in respect to loudness with example and please also describe pitch and frequency
 
iamLbert

iamLbert

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sourov97 said:
sorry!..i was not present here earlier!...but one more ques!....it say "expands little when heated"..if u dont mind!
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expand little more difficult to break, while expand great more easy to break, therefore the answer is thin and expand little (D)
 
Saad Mughal

Saad Mughal

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bubbles1997 said:
Aoa. Help me what is amplitude in respect to loudness with example and please also describe pitch and frequency
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The higher the amplitude of a sound, the louder it is. If you shout, the amplitude of the sound is high whereas if you whisper, the amplitude is low.
If the frequency is high, then the pitch is also high, and vice versa, pitch pitch can be taken from the screeching sound that some animals make whereas low pitch is when you have a sore throat.
 
iamLbert

iamLbert

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Salman Rahman said:
i cant get u...y thin...it say expands a little..so whats the porb using thick...much fragile!
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"Half of the candidates opted for B or C, suggesting that they did not realise that it is the expansion difference between the surfaces which leads to the cracking of the glass. Many of the lower-scoring candidates chose B, thinking that thick glass would be less fragile, while some of the higher-scoring ones chose C" I understood that concept from this quote which comes from the ER, I don't understand quite well...





 
A

Amnaa

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Saad Mughal said:
4. Density = Mass/Volume.
Density = 27/30
Density = 0.9 g/cm3.

6. The mass is in a state of rest so resultant force = 0.

16, Look, a thick wall means that the glass will not reach the surrounding temperature properly, which means that there will be unequal expansion. So to prevent this, we will use a thin wall, now, if it expands greatly on heating than the rise in temperature will cause it to break so the best option should be thin and expands little.

23, Iron is easily magnetized and copper is a non-magnetic material. M and L should be iron (so that they are magnetized easily by a current and other magnet), whereas S (since it stops the armature from being attracted) should be a non-magnetic material which is only copper in the choices.

31, They've asked for D.C. motor and it's a commutator (split ring commutator) that reverses the direction of current to ensure a uniform rotation of the wire.

34, An alternating current is induced since the magnet moves to and fro (that is forward and magnet) and from Fleming's Right Hand Rule we can tell that the current induced is in opposite direction each time so the graph of alternating current would be there. The graph of alternating current is a COSINE graph so option A should be correct.

37, Well, this is easy, we bombard the Uranium - 235 atom with neutrons to make it unstable and cause a fission reaction so C should be the answer.

38, Well, A is incorrect, and so is B, Half life means that after x minutes the isotope would have become HALF be decaying; D is also wrong because after 2 minutes the CURRENT half life would turn half, so after 4 minutes, the isotope would be (1/2)^2 = 1/4 of the original.

40, Well, it's A because the experiment observed the concentrated mass of a Nuclei; this is a fact.
Click to expand...

i did the same in question no.4 but the marking scheme says 9.0g/cm3
 
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