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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: abd123 on March 02, 2011, 07:48:13 pm

Title: Physics Questions.
Post by: abd123 on March 02, 2011, 07:48:13 pm
i came across with this question, i need help with this please :). More questions might come soon  :D

A nuclear scientist has prepared equal quantities of two radioisotopes, 211-Bi and 215-Bi. The
sample of Bismuth-211 initially has four times the activity of the bismuth-215 sample. The half-life of
bismuth-211 is equal to 2 min. Which of the following statements is true?

A) These isotopes have half-lives of 2 and 8min, respectively.
B) These isotopes have have half-lives of 8 and 2min, respectively.
C) These isotopes have identical half-lives because they contain the same element.
D) These isotopes have half-lives of 2 and 32 min, respectively.
Title: Re: Physics Questions.
Post by: /0 on March 03, 2011, 01:24:56 am
I would say A.
4 times the activity means 4 times the decay rate

Though I haven't done nuclear in a long time >_>
Title: Re: Physics Questions.
Post by: Killerkob on March 03, 2011, 08:39:24 pm
I'd assume it would be something to do with the structure of the atom and how the electro-magnetic force keeps the electrons in orbit as opposed to colliding with the nuclei. Or possibly that beryllium-7 has a high ionising ability and therefore is more able to pass through matter, effectively 'dodging' the electrons.

Not too sure.
Title: Re: Physics Questions.
Post by: schnappy on March 03, 2011, 08:47:42 pm
The electron cloud (You can use that term literally or metaphorically I suppose) will repel the inbound electron, deflecting it.

I think.
Title: Re: Physics Questions.
Post by: schnappy on March 05, 2011, 01:13:32 pm
And you want to do theoritical physics?

:S
Title: Re: Physics Questions.
Post by: /0 on March 05, 2011, 05:08:29 pm
Quote from: schnappy on March 05, 2011, 01:13:32 pm
And you want to do theoritical physics?

:S

Woah, he's only year 11... and anyway it never hurts to ask questions if you're unsure
Title: Re: Physics Questions.
Post by: /0 on March 14, 2011, 10:39:32 pm
Electrostatic force is given by , where is the electric field and is the charge of the object.

For the electron, we have and , allowing us to solve for .

We can then use to find the force on the alpha particle.