Physics: Post your doubts here!

[awesomaholic101]

Can someone tell me how to measure % uncertainty in a stopwatch

For example i did an oscillation experiment and got time taken 28.05 seconds

how to calculate % uncertainty ?

ur stopwatch reads to the nearest 0.01 s ... so uncertainty of ur reading would be : 0.01/2 = 0.005
so %uncertainty in ur reading = (0.005/28.05)*100 = 0.02%

 

[Xtreamer]

Oh God it sure did!!
24 hrs should be over rite?

Where you guys discussing?

 

[awesomaholic101]

Where you guys discussing?

uhh no ... anyway plz temme the width was NOT 2w!!! coz i wrote 2w and changed it to √2 w

 

[Hassan Ali Abid]

View attachment 54980
2(a) (ii) number 2 for acceleration.

From marking scheme :

mg – F = ma hence a = g – [F / m]
m = ρ × V = ρ × 4/3 π R3 = (1.4 × 10–5) C1
a = 9.81 – [6.9 × 10–5] / ρ × 4/3 π × (1.5 × 10–3)3 (9.81 – 4.88) M1
a = 4.9(3) m s–2

How ? and why we got/used this equation mg – F = ma ? why why not mg + f= ma not used ? why the minus sign

weight is acting downwards,since the drop is moving down so the friction will acting in the opposite direction ie upwards , therefore
net force = W-F
ma=mg-f

where w=mg
and net force = ma.

 

[shinnyyy]

Im stuck in Hall voltage and hall probe concept and i cant find these two topics in Cambridge endorsed book so can anyone suggest me how to cover those two topics and how to understand these concepts?

 

[Xtreamer]

uhh no ... anyway plz temme the width was NOT 2w!!! coz i wrote 2w and changed it to √2 w

LOL i dont remember that one i did tukka so....do u remember the exact question? if so we can search it

 

[Xtreamer]

Im stuck in Hall voltage and hall probe concept and i cant find these two topics in Cambridge endorsed book so can anyone suggest me how to cover those two topics and how to understand these concepts?

Is that from A2 syllabus?

 

[Wolfgangs]

"A turbine at a hydroelectric power station is situated 30 m below the level of the surface of a large
lake. The water passes through the turbine at a rate of 340 m3 per minute.
The overall efficiency of the turbine and generator system is 90%.
What is the output power of the power station? (The density of water is 1000 kg m–3.)
A 0.15 MW B 1.5 MW C 1.7 MW D 90 MW"

Can someone please help me with this question? How is the answer B?

 

[shinnyyy]

Is that from A2 syllabus?

yes its from A2 syllabus and i have seen some papers and i can see the questions from these topics but idk how to solve and approach those questions.

 

[awesomaholic101]

LOL i dont remember that one i did tukka so....do u remember the exact question? if so we can search it

don't remember the exact question :/ ... thou it had sth to do with resistance ...

 

[Xtreamer]

yes its from A2 syllabus and i have seen some papers and i can see the questions from these topics but idk how to solve and approach those questions.

I wish i could help you but i havent started to study for A2...check out youtube...look for physics topics by Khan Academy that might help you

 

[Xtreamer]

don't remember the exact question :/ ... thou it had sth to do with resistance ...

Q34. The stress is reduced is directly proportional to thickness of wire w. When w is halved, what is the stress?

this was this question right? i looked it up but it hasnt been repeated wait i will ask some other people

 

[awesomaholic101]

Q34. The stress is reduced is directly proportional to thickness of wire w. When w is halved, what is the stress?

this was this question right? i looked it up but it hasnt been repeated wait i will ask some other people

No, not that one .... i am talking about the wire and the thickness of its wall ... but anyway, i'd like to know this one as well

 

[Xtreamer]

No, not that one .... i am talking about the wire and the thickness of its wall ... but anyway, i'd like to know this one as well

Yaar my friends don't want to discuss paper but they don't remember the answers to those questions as well...CHILL sab nay tukka maara hai XD relax and enjoy CHUTIYAAAN!

 

[awesomaholic101]

Yaar my friends don't want to discuss paper but they don't remember the answers to those questions as well...CHILL sab nay tukka maara hai XD relax and enjoy CHUTIYAAAN!

Hehehe ... I know no-one wants to ...

 

[shinnyyy]

try to see the worked solutions about this topic at
http://physics-ref.blogspot.com/2014/05/physics-9702-notes-worked-solutions-for.html

see how they are solved, maybe this would help. hall probe is only an applications of electromagnetism

Thank you so much for helping.

 

[shinnyyy]

try to see the worked solutions about this topic at
http://physics-ref.blogspot.com/2014/05/physics-9702-notes-worked-solutions-for.html

see how they are solved, maybe this would help. hall probe is only an applications of electromagnetism

Thank you so much for helping.

 

[shinnyyy]

guys I need help in this question

question 9 from oct/nov 2010 paper 13:

9 A body, initially at rest, explodes into two masses M1 and M2 that move apart with speeds v1 and v2 respectively.
What is the ratio v1/v2?

 

[Wkhan860]

guys I need help in this question

question 9 from oct/nov 2010 paper 13:

9 A body, initially at rest, explodes into two masses M1 and M2 that move apart with speeds v1 and v2 respectively.
What is the ratio v1/v2?

Its B ....M2/M1
Momentum bfr explosion is 0
so.... 0=M1V1-M2V2
Make V1/V2 subjeact...nd u get M2/M1 as ans

 

[shinnyyy]

I need the working and explaination for these two questions.plz help me