A rock falls to the ground with a force of 300N and air resistance pushes back up on the rock with a force of 45N. Which is true of the rock?
A There are balanced forces acting on the rock and the net force is 255N down
B. There are unbalanced forces acting on the rock and the net force is 255N down
C. There are balanced forces acting on the rock and the net force is 345N down
. There are unbalanced forces acting on the rock and the net force is 345N down

Which of the following correctly describes what happens when an atomic bomb explodes? small pieces of fissionable material are joined and form a body with a mass greater than the critical mass, the relative number of neutrons escaping decreases, and a chain reaction and explosion result. large pieces of fissionable matter are brought together quickly and form a body with a mass smaller than the critical mass, the relative number of escaping neutrons increases, and a chain reaction and explosion result.