You are Here: Home >< Physics

# Quick rate of decay qs watch

1. Last part what equation we using?

Power = work done/time?

And what are we trying to find.
Attached Images

2. Also the question after asks me to work out the mass.

Why is the mr 0.239?
3. well if each decay gives 8.2x10-13 Joules, yes you would need to use P=e/t, and dN/dt = A = LambdaN.
(
)The rate of decay x the energy per decay would give you the power. So set up the equation A x 8,2x10-13=2.5,

Mr is always stated a grams per mol, so 0.239 is the mr of Plutonium in kg
4. Bq is number of decays per second
W is Joules per second

each decay releases 8.2E-13 J of energy
how many decays per second are needed to release 2.5J per second?
5. (Original post by Formless)
well if each decay gives 8.2x10-13 Joules, yes you would need to use P=e/t, and dN/dt = A = LambdaN.
(
)The rate of decay x the energy per decay would give you the power. So set up the equation A x 8,2x10-13=2.5,

Mr is always stated a grams per mol, so 0.239 is the mr of Plutonium in kg
Cheers
6. AQA?
7. (Original post by Joinedup)
Bq is number of decays per second
W is Joules per second

each decay releases 8.2E-13 J of energy
how many decays per second are needed to release 2.5J per second?
Would this be alright?
8. (Original post by Formless)
AQA?
OCR, ****ing hate physics man.
9. (Original post by Super199)

Would this be alright?
it's a 'show that' question... probably a one marker
I'd probably have said

Power = energy per decay * number of decays per second
2.5 = (8.2×10-13) * (3.0×1012) (to 2 s.f.)

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: June 19, 2017
Today on TSR

### Congratulations to Harry and Meghan!

But did you bother to watch?

### What do you actually do at University?

Poll

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE