Asample is in the second half-life. what percent of the sample is stable at this point?

12.5%
25%
50%
75%

-- At the end of the first half-life, 50% of the sample is stable.

-- At the end of the second half-life, an additional half of the remaining half
will be stable = 75%.

-- During the second half-life, the stable -portion is somewhere
between 50% and 75%.

1) when you rub your hands together quickly, the kinetic energy is converted to mechanical energy.2) thermal energy from the sun travels to earth as infrared waves.3) energy is transferred through the matter of space by electromagnetic waves. 4) when a match is burned, chemical potential energy is converted to thermal and radiant energy. 5) seismicwaves are caused by back and forth movement , or vibration, of an object. 6) mechanicalenergy in an engine changes thermal energy into kinetic energy to make a car move.