Physics: Post your doubts here!

[Student12]

yeah will do it tonight

Thanks

 

[mehria]

Do some of them at least or by tonight.. :/ i know you have to prepare.

wait.. m gonna solve them... but i need sumtym

 

[Student12]

View attachment 45255

Ep = mgh = (h/4) ( h/2 is the height from m the midpoint to the depth)= mgh/4

 

[ashcull14]

if the rate is

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w12_qp_13.pdf

question 21


thought blocker????

constant then the kinetic energy would be zero...as it loses gpe....so only option left is B

 

[Zepudee]

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

ANS: B

 

[ashcull14]

Ep = mgh = (h/4) ( h/2 is the height from m the midpoint to the depth)= mgh/4

thnks

 

[unique111]

3)
the derived unit of a volt is defined with units W.A-1, and the derived unit of a watt (W) is defined in J.s-1
Now do it your self

5)
Uncertainty unique111

Q5) V=5*2*1=10
Uncertainty in V= (0.01/5+0.01/5+0.01/1)*10=0.17
Density=m/v=25/10=2.5
Uncertainty in D= (0.1/25 + 0.17/10)*2.5=0.0525=0.05

 

[ashcull14]

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

ANS: B

E=mgh
m=d*V
1000*340=340000kg
E=340000*9.8*30=99.9*10^6J
input power=99.9*10^6/60=1.6*10^6W
output/1.6*10^6*100=90
output power=1.49*10^6W

 

[AhsanAfzal]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w13_qp_13.pdf
Q33 how do we know the speed of electrons?

 

[Zepudee]

E=mgh
m=d*V
1000*340=340000kg
E=340000*9.8*30=99.9*10^6J
input power=99.9*10^6/60=1.6*10^6W
output/1.6*10^6*100=90
output power=1.49*10^6W

AHHH thank you so so much!!!

 

[ashcull14]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w13_qp_13.pdf
Q33 how do we know the speed of electrons?

maybe bcz...resistance is greater in thin copper wire as it is inversley proportional to cross sec area....so speed of e should be greater in thicker wire and less in thin wire..asgreater the resistance lesser the speed

 

[ashcull14]

cn someone plx solve it

 

[danial 234]

View attachment 45263
cn someone plx solve it

900*0.2=F*1.2
solve to find F

 

[Snowysangel]

Force = density * area * velocity^2
=1.2*12*(33^2)

Bit how do u derive that equation using f=ma?

 

[Rockstar RK]

Somebody solve dis: Winter 2008's Q-10

 

[nononona]

june 2003 please explain numbers :
10
11
13
19
20
22
28
29
35 why not b
36?????

 

[Asad Moosvi]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w04_qp_1.pdf

Question 20 please

 

[ashcull14]

help

 

[ashcull14]

use

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w04_qp_1.pdf

Question 20 please

the formula d1/d2=h2/h1
hq/hp=2/3

 

[Snowysangel]

plz explain the scenario at Y. i cant figure it outView attachment 45254

I think it's cause the total kinetic energy remains the same at Y. The sand is dropped with some velocity too