Edexcel PHYSICS Doubts

[astarmathsandphysics]

It is the correct answer according to my calculation. I made it 1.45*10^-3

[dk bose]

Sorry sir, i made a mistake finding it ,but now i got it!!! here's my next question -
A 2.2*10^-6F capacitor is charged to a potential difference of 15V, and a 3.3*10^-6F capacitor is charged to a potential difference of 30V.
a)Calculate -  1)the charge on each capacitor,  2)the energy stored by each capacitor.
b)Show that, once Charge has re-distributed, the ratio of charge on each capacitor is equal to the ratio of the two capacitances. Hence calculate the charge on each capacitor and the final potential difference.
c)Calculate the total energy stored by the capacitors and suggest why this is less
than the total energy that would be stored by the capacitors individually.

[astarmathsandphysics]

the capacitor q answers

[dk bose]

A student is designing an alarm circuit. She wants a time interval between closing a switch and the circuit becoming active. She decides to charge a 2200*10^-6F capacitor through a resistor from a 5V supply. The potential difference across the capacitor must rise to 4.3V for the alarm circuit to become active.
Calculate the size of the resistor that she should connect in the circuit to achieve a 1 minute delay.

[astarmathsandphysics]

Solve V=V_0 e^{-t/RC)
4.3=5e^-60/(R*2.2*10^-3))
4.3/5=0.86 =e^-60/(R*2.2*10^-3))
-60/(R*2.2*10^-3)) =ln 0.86=-0.151
R=180000 ohms

[dk bose]

Sir,sorry to say but you will have to try the sum again as the answer is wrong.the correct answer is 14*10^3 ohm.

[dk bose]

Protons are accelerated to an energy of 10 GeV and the beam is made to collide head-on with a beam of anti-protons, also with an energy of 10GeV. How much energy is available from each collision to produce new particles?Take the proton mass as 940 MeV/C^2.

plzz solve this sum and give the solutions as fast as possible.!!!!

[astarmathsandphysics]

20GeV
Checked the previous answer and get the same

[dk bose]

sir,this answer is wrong too.its 21.9GeV.plzz try to solve the sum again.

[The Golden Girl =D]

Just out of curiosity , How come a Strong Magnet is NOT attracted to a (Hollow) Copper tubing even though it's a Metal o.O ?

It is demonstrated in this video =>   http://videosift.com/video/Magnet-Slowly-Falling-in-Copper-Pipe

Thanks in Advance =D

[astarmathsandphysics]

(10+.94)*2 but they include rest mass of protons which I did not

[astarmathsandphysics]

Copper notmagnet

[AS01]

I am sitting for my As first module exam for physics i finished doing all past papers that i can find. now i don't even have anything to do. can someone plz give me the or something where i can find  lots of question on physics?

[astarmathsandphysics]

I emailed you

[The Golden Girl =D]

I still don't get why they don't attract =/ !?

thanks again =D