Physics: Post your doubts here!

[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)/

 

[I Believe]

Why is the answer B?

 

[Thought blocker]

View attachment 61396
Why is the answer B?

What else can b the answer?

 

[Thought blocker]

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

Which part of that question?

 

[I Believe]

What else can b the answer?

It's strange because when sand is added, the velocity decreases but when it leaves, makes no difference?!

 

[Thought blocker]

It's strange because when sand is added, the velocity decreases but when it leaves, makes no difference?!

Just imagine when u are driving a car slowly when someone will sit in this running car, the speed will decreases, but when that person leaves the car, why the hell the speed will change xD Getting what m tryna say?

 

[I Believe]

Just imagine when u are driving a car slowly when someone will sit in this running car, the speed will decreases, but when that person leaves the car, why the hell the speed will change xD Getting what m tryna say?

no no...I disagree, in fact totally disagree
If a person's coming into car decreased it's speed then his going away must increase the speed
why shouldn't it?