If a radioisotope has a half life of 10 years, how much of the original material would remain after 40 years?

What is the cellular process that releases the energy stored in food molecules

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

The twister and runaway train are two coasters at the same amusement park. both coasters start at the same height. the coaster for the twister is twice the mass of the coaster for the runaway train. which roller coaster has greater gravitational potential energy at the start of the ride?