The half-life for the radioactive decay of u-238 is 4.5 billion years and is independent of initial concentration. how long will it take for 10% of the u-238 atoms in a sample of u-238 to decay? if a sample of u-238 initially contained 1.5×10181.5×1018 atoms when the universe was formed 13.8 billion years ago, how many u-238 atoms does it contain today?

Lymphocytes known as blastocysts make antibodies that fight infection. select the best answer from the choices provided t f

Mutt and jeff are running along a path each pushing a cart loaded with rocks. if mutt's wagon has a mass two times greater than jeff's and they want to stay together, arriving at their destination at the same time, what must happen? a) jeff should slow down so mutt can catch up. b) mutt must use half as much force to push his cart. c) mutt must use twice as much force to push his cart. d) mutt and jeff will use the same force, but mutt will take bigger steps.

Amoving electron has kinetic energy k1. after a net amount of work w has been done on it, the electron is moving one-quarter as fast in the opposite direction. (a) find w in terms of k1. (b) does your answer depend on the final direction of the electron's motion?