Physics: Post your doubts here!

[Thought blocker]

Can anyone help me with Sociology notes here?

https://www.xtremepapers.com/community/threads/a-level-psychology-sociology-help.32260/#post-837731

The one who upload notes, ask for more help from him/her.

Here we can only hep for physics though.

 

[Thought blocker]

http://dynamicpapers.com/wp-content/uploads/2015/09/9702_m16_qp_42.pdf
Q5(b)

 

[RICK SHARMA]

The density of air on the Earth decreases almost linearly with height from 1.22 kg m –3 at sea level
to 0.74 kg m –3 at an altitude of 5000 m.
Atmospheric pressure at the Earth’s surface on a particular day is 100 000 Pa. The value of g
between the Earth’s surface and an altitude of 5000 m can be considered to have a constant
value of 9.7 m s –2 .
What will be the atmospheric pressure at an altitude of 5000 m?
OPTIONS:
36000 Pa
48000 Pa
54000 Pa
59000 Pa
How is this done....been scratching my head for an hour now...

 

[I Believe]

 

[The Sarcastic Retard]

View attachment 61218

C ?

 

[The Sarcastic Retard]

The density of air on the Earth decreases almost linearly with height from 1.22 kg m –3 at sea level
to 0.74 kg m –3 at an altitude of 5000 m.
Atmospheric pressure at the Earth’s surface on a particular day is 100 000 Pa. The value of g
between the Earth’s surface and an altitude of 5000 m can be considered to have a constant
value of 9.7 m s –2 .
What will be the atmospheric pressure at an altitude of 5000 m?
OPTIONS:
36000 Pa
48000 Pa
54000 Pa
59000 Pa
How is this done....been scratching my head for an hour now...

my answer is 52000Pa

 

[I Believe]

C ?

yep can you explain how?
I thought it was B because Y is the vertical component (Fsinθ ) and X is the horizontal component (Fcosθ) so a larger value of θ gets us a larger value of cosθ and larger value of θ results in smaller value of sinθ, isn't it?

 

[Thought blocker]

yep can you explain how?
I thought it was B because Y is the vertical component (Fsinθ ) and X is the horizontal component (Fcosθ) so a larger value of θ gets us a larger value of cosθ and larger value of θ results in smaller value of sinθ, isn't it?

use ur calc.. u will get to know.

 

[Thought blocker]

http://dynamicpapers.com/wp-content/uploads/2015/09/9702_m16_qp_42.pdf
Q5(b)

?

 

[RICK SHARMA]

my answer is 52000Pa

yes you are right....can you please explain how?

 

[i_try9621]

Ques 8) c) ii) what will be the molar mass and why?

 

[Thought blocker]

Ques 8) c) ii) what will be the molar mass and why?

You calculated the activity in part (i) / decay constant = Number of molecules.
1 mol = 6.02 * 10 ^23 moleculs
then how many moles in activvity calculated in (i) / decay constant?
Then now u have number of moles, u can calculate mass.
mass = Mr * n
mass = 89 * n

 

[kungfuPanda]

HI Guys can someone explain this question and solution to me
Steel wire is stretched in an experiment to determine Young modulus for steel.
Uncertainties in the measurements are given below.
measurement uncertainty
load on wire ±2%
length of wire ±0.2%
diameter of wire ±1.5%
extension ±1%
What is the percentage uncertainty in Young modulus?
A 1.3% B 1.8% C 4.7% D 6.2%
Answer: D.
Young modulus, E = stress / strain = (F/A) / (e/L) = FL / Ae
where F is the load on the wire, L is the length of wire, A is the cross-sectional area of the wire and e is the extension

Cross-sectional area of wire = πd2 / 4
where d is the diameter of the wire

Young modulus, E = 4FL / πd2e
(ΔE / E) x 100% = [(ΔF / F) + (ΔL / L) + 2(Δd / d) + (Δe / e)] x 100%
Percentage uncertainty, (ΔE / E) x 100% = 2 + 0.2 + 2(1.5) + 1 = 6.2%
Guys can someone Pls tell me wtf happened to the 100%?Since its a percentage aren't we supposed to multiply it?
The answer to this question we leave the 100% on the left side -_-??
helppppp pls

 

[Thought blocker]

HI Guys can someone explain this question and solution to me
Steel wire is stretched in an experiment to determine Young modulus for steel.
Uncertainties in the measurements are given below.
measurement uncertainty
load on wire ±2%
length of wire ±0.2%
diameter of wire ±1.5%
extension ±1%
What is the percentage uncertainty in Young modulus?
A 1.3% B 1.8% C 4.7% D 6.2%
Answer: D.
Young modulus, E = stress / strain = (F/A) / (e/L) = FL / Ae
where F is the load on the wire, L is the length of wire, A is the cross-sectional area of the wire and e is the extension

Cross-sectional area of wire = πd2 / 4
where d is the diameter of the wire

Young modulus, E = 4FL / πd2e
(ΔE / E) x 100% = [(ΔF / F) + (ΔL / L) + 2(Δd / d) + (Δe / e)] x 100%
Percentage uncertainty, (ΔE / E) x 100% = 2 + 0.2 + 2(1.5) + 1 = 6.2%
Guys can someone Pls tell me wtf happened to the 100%?Since its a percentage aren't we supposed to multiply it?
The answer to this question we leave the 100% on the left side -_-??
helppppp pls

I am not getting what is your doubt.
that (ΔE / E) x 100% is the percentage uncertainity of E. Thats what we found and that is the answer. What u not getting?

 

[kungfuPanda]

I am not getting what is your doubt.
that (ΔE / E) x 100% is the percentage uncertainity of E. Thats what we found and that is the answer. What u not getting?

HAHAHAHA lol
I'm not getting this line (ΔE / E) x 100%
We calculate 2 + 0.2 + 2(1.5) + 1=6.2 Right?
Then aren't we supposed to multiply the bit by 100??
What happens to the 100 why we ignore it,Where did it go? -_-

 

[kungfuPanda]

Isn't the formula for Percentage uncertainty= Change in value/Orignal value xTimes 100?

I am not getting what is your doubt.
that (ΔE / E) x 100% is the percentage uncertainity of E. Thats what we found and that is the answer. What u not getting?

 

[Thought blocker]

Isn't the formula for Percentage uncertainty= Change in value/Orignal value xTimes 100?

The formula for percentage error is :
(ΔE / E) x 100% = [(ΔF / F) + (ΔL / L) + 2(Δd / d) + (Δe / e)] x 100%
Where "(ΔE / E) x 100%" This is what we hav to find.
(ΔE / E) x 100% means the PERCENTAGE UNCERTAINITY of E!

 

[kungfuPanda]

The formula for percentage error is :
(ΔE / E) x 100% = [(ΔF / F) + (ΔL / L) + 2(Δd / d) + (Δe / e)] x 100%
Where "(ΔE / E) x 100%" This is what we hav to find.
(ΔE / E) x 100% means the PERCENTAGE UNCERTAINITY of E!

lolol ohhh
Well
There is also a direct approach to this question by using the youngs modulus matric for steel which is 2.lol
No need for the long explanation Usuallay in these typo questions
I guess we don;t multiply because the question say's we are trying to find the percentage uncertainty in not "of" meaning that we are finding the amount not the determined percentage itself.
lol thanks bro

 

[Thought blocker]

lolol ohhh
Well
There is also a direct approach to this question by using the youngs modulus matric for steel which is 2.lol
No need for the long explanation Usuallay in these typo questions
I guess we don;t multiply because the question say's we are trying to find the percentage uncertainty in not "of" meaning that we are finding the amount not the determined percentage itself.
lol thanks bro

Anytime!

 

[areeba240]

can some one plzz explain me the qtn 1 of june 2016 p42
http://papers.gceguide.com/A Levels/Physics (9702)/