Which principle states that the processes occurring on earth today are the same as those that occurred in the past?

a. principle of uniformitarianism
b. principle of superposition
c. principle of fossil correlation
d. principle of original horizontality

The twister and runaway train are two coasters at the same amusement park. both coasters start at the same height. the coaster for the twister is twice the mass of the coaster for the runaway train. which roller coaster has greater gravitational potential energy at the start of the ride?