You drop a rock down a well that is 31 m deep. How long does it take the rock to hit the bottom of the well?
O A. 1.9 s
O B. 6.3 s
O c. 2.75
O D. 2.5 s

Which statements best describe the work of marie and pierre curie? check all that apply. they discovered radioactivity. they came up with the term “radioactivity.” they conducted experiments with uranium-containing minerals and pure uranium. they conducted experiments with uranium-containing minerals and photographic plates. they discovered two new radioactive elements.