Qualification > Sciences
ALL PHYSICS DOUBTS - POST HERE !!
igext:
--- Quote from: 33oomar on May 25, 2010, 07:48:29 pm ---Guys.. I need help in
question 39 may/june 2007 paper 1
Please help meeeeee :(
--- End quote ---
20 hours means 4 half lives so double the value present now 4 times ( x2 x2 x2 x2 )
Vin:
--- Quote from: Adzel on May 25, 2010, 07:45:24 pm ---see attached...
--- End quote ---
ok so density = mass/volume
in the diag . the initial volume if 100 cc after pouring the liquid its 140 to mass of water = 140 - 100 = 40 cc
volume on diag is 60 cc
density = mass/volume
=40/60
Vin:
--- Quote from: igext on May 25, 2010, 07:44:17 pm ---my teacher said the current is directly induced in the 2ndry coil with out the help of the core
--- End quote ---
nop .. not possible ..
igext:
--- Quote from: ~VIN1094~ on May 25, 2010, 07:52:10 pm ---nop .. not possible ..
--- End quote ---
now there is an alternating field due to the 2ndry coil? why duznt this affect the current in primary coil?
Shazizzzle:
--- Quote from: 33oomar on May 25, 2010, 07:48:29 pm ---Guys.. I need help in
question 39 may/june 2007 paper 1
Please help meeeeee :(
--- End quote ---
The half-life is 5 hours. That means it takes 5 hours for half the sample to decay.
They are asking about 20 hours before.
After the 20 hours, it was 0.48 g.
How much was it 5 hours before? It would be double, as 5 hours is the half life.
So, 0.48 X 2= 0.96.
0.96 was 5 hours before.
What about ten hours before the initial?
That would be double of the 5 hours before one. i.e 0.96 X 2 = 1.92.
So, 10 hours ago, it was 1.92.
What about 15 hours before? That would be 5 more behind the 10 hours one.
So, 1.92 X 2 = 3.84
And thus for 20, 3.84 X 2 = 7.68
See, in every 5 hours, it doubles.
You can't just multiply 0.48 by 4.
It DOUBLES every 5 HOURS.
So, you have to double it, in each step, when going backwards.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version