Which of the following is an example of radiation?
a. a metal spoon becomes warm after being set in a pot of boiling water.
b. warm water rises because it is less dense than cool water.
c. pancake batter cooks quickly after being spooned onto a hot griddle.
d. our atmosphere is constantly being heated by the sun.

b.a device that inputs heat into a cool object

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.