two scientists are experimenting with pure samples of isotope x, a highly radioactive substance. the first scientist has a sample with a mass of 20 grams. he measures a half-life of 232 seconds. the second scientist has a sample of the same substance with a mass of 80 grams. what is the half-life that she is most likely to measure?
a. 58 seconds
b. 232 seconds
c. 464 seconds
d. 928 seconds

Astone is thrown with a speed v0 and returns to earth, as the drawing shows. ignore friction and air resistance, and consider the initial and final locations of the stone. which one of the following correctly describes the change δpe in the gravitational potential energy and the change δke in the kinetic energy of the stone as it moves from its initial to its final location? options a.δpe = 0 j and δke = 0 j b.δpe is positive and δke is negative c.δpe = 0 j and δke is positive d.δpe is negative and δke is positive e.δpe = 0 j and δke is negative