How many half-lives have passed if a sample contains 25% of its original carbon-14? 1 half-life
2 half-lives
3 half-lives
4 half-lives

Ahypothesis is? close agreement by competent observers of observations of the same phenomena. a guess that has been tested over and over again and always found to be true. an educated guess that has yet to be proven by experiment. the long side of a right triangle. a synthesis of a large collection of information that includes guesses.

An object moves from the position +34m to the position -15m in 15 seconds. what is it's total displacement? what is it's average velocity?

The energy released by a nuclear fusion reaction is produced when