What happens at the beginning of every roller coaster ride?.

Which is the best for showing percentages of different types of cars sold(gas hybrid , electric , other ) in the united states ?

When a spring is compressed, the energy changes from kinetic to potential. which best describes what is causing this change? work power gravitational energy chemical energy

Several mountains together form a mountain . a few of these combined form a mountain system. several systems combined form a mountain , which can stretch thousands of miles in length.