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Physics: Post your doubts here!

asd

asd

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Jiyad Ahsan said:
righto
mass of a person = around 70kg
height of a person = 1.5m
density of water = 300 cm^3
weight of an apple = 1N
typical current in domestic appliances = 13 A
e.m.f of a car battery = 12 V
density of air at STP = 1.293 kg/m^3

since the wavelength and frequencies are related by V=freq. x wavelength, and since v of all E.M waves is 3.0 x 10^8
just remember one of them.. i'll put them up
Click to expand...
Dont forget these (they're the ones that I came across while solving the past papers and are not mentioned in the book :p) :
mass of a nucleus: 1*10^-25 kg
radius of a nucleus: From 1*10^-15 - (1*10^-14) m
radius of a proton = radius of a neutron = 1*10^-15 m
size of an atom: 1*10^-10 m
size of a molecule: From (1*10^-10) - (1*10^-6) m
and just rattafy the values of either the wavelengths or frequencies, cause you can calculate the other quantity if you know any one of them (since speed of light is already known)
Oh and also the questions that require you to calculate the mass of a nucleus, we multiply unified atomic mass constant with the number of the nucleons.
well, (y) if you already know this, I just wanted to share this cause I used to multiply the atomic number with the rest mass of a proton and the number of neutrons with the unified atomic mass constant and then add the both since I thought protons and neutrons have their own different masses. But for a nucleus, we assume the Nucleons (protons and neutrons both) have the same mass of 1.66*10-27.
 
daredevil

daredevil

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asd said:
Dont forget these (they're the ones that I came across while solving the past papers and are not mentioned in the book :p) :
mass of a nucleus: 1*10^-25 kg
radius of a nucleus: From 1*10^-15 - (1*10^-14) m
radius of a proton = radius of a neutron = 1*10^-15 m
size of an atom: 1*10^-10 m
size of a molecule: From (1*10^-10) - (1*10^-6) m
and just rattafy the values of either the wavelengths or frequencies, cause you can calculate the other quantity if you know any one of them (since speed of light is already known)
Oh and also the questions that require you to calculate the mass of a nucleus, we multiply unified atomic mass constant with the number of the nucleons.
well, (y) if you already know this, I just wanted to share this cause I used to multiply the atomic number with the rest mass of a proton and the number of neutrons with the unified atomic mass constant and then add the both since I thought protons and neutrons have their own different masses. But for a nucleus, we assume the Nucleons (protons and neutrons both) have the same mass of 1.66*10-27.
Click to expand...
jalisjdfiajflsf.... waT?? o_O :confused: :sick:
wat wsa that about nucleus and stuff... can you post a question like that and also eplain it a bit puhllleeezzz!!
 
Beaconite007

Beaconite007

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asd said:
Yeah I have the same problem, but what I always do is consider the curve as a straight line which doesnt always give the exact answer. :p
Click to expand...
True, might as well do that and add/subtract a random number from it.
We only have 1 hour for this paper, can't expect us to stay on one question's one part for 5 mins :s
And besides, my eyes give away and I forgot which blocks I counted and which ones I left out.
Not to mention some are half, a quarter or 3 quarters >_>
 
Jiyad Ahsan

Jiyad Ahsan

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daredevil said:
jalisjdfiajflsf.... waT?? o_O :confused: :sick:
wat wsa that about nucleus and stuff... can you post a question like that and also eplain it a bit puhllleeezzz!!
Click to expand...
umm the mass of a neutron or a proton is given(something around 1.67x10^-27 kg)... so if they ask you to find the mass of lets say of carbon you know there are 6 protons and 6 neutrons so just add em.. like (6 x mass of proton) + (6 x mass of neutron)
 
ZainH

ZainH

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Beaconite007 said:
But wouldn't that give a slightly greater/lesser value than the actual?
Click to expand...

Yeah it would, but theres usually a range of values when it comes to finding the area under a curve.
If you're feeling unsure about the area of the triangle just make the approximation sign and write your value OR add/subtract a reasonable amount from it.
 
asd

asd

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Jiyad Ahsan said:
umm the mass of a neutron or a proton is given(something around 1.67x10^-27)... so if they ask you to find the mass of lets say of carbon you know there are 6 protons and 6 neutrons so just add em.. like (6 x mass of proton) + (6 x mass of neutron)
Click to expand...
Thats exactly what I told you NOT to do. :D
I checked the ms, they just use the UNIFIED ATOMIC MASS CONSTANT for both. so if you have like 12 nucleons, regardless of whatever the number of protons is, you multiply 12 by 1.66*10^-27
 
asd

asd

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ZainH said:
Yeah it would, but theres usually a range of values when it comes to finding the area under a curve.
If you're feeling unsure about the area of the triangle just make the approximation sign and write your value OR add/subtract a reasonable amount from it.
Click to expand...
have you tried the method? like does it give the value anywhere close to the answer?
cause I dont think it does :p
 
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