Most radiation exposure comes from natural sources. These so-called "natural sources" include Radon, Internal, Terrestrial, and Cosmic. Among that, Radon proves to be the largest source of radiation. Radon is a naturally occurring radioactive gas that comes from the breakdown of uranium.
When energy is emitteds by a source and travels through a medium until it's absorbed by matter, radiation is occuring. We are exposed to radiation everyday, some sources of radiation are natural and other come from man-made elements. We are commonly exposed to Background radiation, from Earth itself (some minerals) and very few man-made objects. From this type of radiation comes the one we are the most exposed to emitted by Radon and Thoron (radioactive gases which are created when other naturally occurring elements undergo radioactive decay). This gases represent 37% of all the radiation we are commonly exposed to.
Consider resistors in a circuit - if all the resistors in the circuit are in series and one of the resistors fails then no current can flow thru the circuit,
If the resistors are in parallel then then each resistor experiences the same voltage drop regardless of whether or not any resistor in particular is carrying current.
I don't think your appendix can explode because you ate too much honestly. It's not even possible to eat so much that your appendix explodes, and if you're feeling any pain it definitely isn't because your appendix is about to explode, believe me. Also you could just type it into the internet, that'd be a much faster solution.
Since velocity vector has 2 components: direction and magnitude, and speed is the velocity's magnitude. So if the velocity doesn't change its direction, we essentially use its magnitude, aka speed, to calculate the rate of change for acceleration.