Sound, balloons, light, & pressure questions

[alliecr]

Homework Statement

Question 1: A gram of radioactive material has a half life of x.

Homework Equations

Please not that this is a generally question and I am not actually solving for X.
After x amount of time, how much will be left?

The Attempt at a Solution

I believe the answer is somewhere along the lines of: The half-life is the time required for half the atoms in the sample to decay.

Question 2: When light reflects from a surface, there is a change in its?
I am not exactly sure what the teacher is wanting for the answer. Any ideas?

Question 3: Gas pressure inside an inflated, stretched balloon is actually____________.
equal, less than, greater than

Question 4: In a vacuum, a marshmallow becomes__________.
My guess is that it becomes bigger.

Question 5: When an alpha particle is ejected from the nucleus, the nucleus has less________. (Charge, mass, both, neither)
My guess would be less charge because the alpha particle is two neutrons and two protons--which have charges.

Question 6: What is the speed of a free falling object--if air resistance is absent--on the 3rd second?
I am not sure of this question at all. Is there a formula for a problem like this?


Please note that I am NOT trying to have someone do my homework for me. I would like explanations of why the answer is the answer. Thanks in advance!


--Allison

 

[LowlyPion]

1. http://en.wikipedia.org/wiki/Half_life

2. Reflect, ... hmmm. Is the light going in the same direction?

3. If the air in the balloon is trying to get out, trying so hard it is stretching the rubber ...

4. Good instinct.

5. Good answer.

6. You're in luck. There are some equations that might help.

https://www.physicsforums.com/showpost.php?p=905663&postcount=2