The thrill of a rollercoaster.
You may be surprised to learn that most rollercoasters don't have engines - instead, they rely on forces to provide an exhilarating ride.
It all starts at the beginning of the ride, with electromagnetic force.
Electromagnets along the track attract or repel magnets attached to the rollercoaster's carriage to propel it forward and give it momentum.
Greg Bryant, Mechanical Engineer - "Old rollercoasters used to have a chain that would pull you to the top of the first drop, the first hill. You'd go clunk, clunk, clunk all the way up and you knew it was coming. But now they use an electromagnetic launch on lots of rollercoasters where you just sit on the rollercoaster and you're going along very slowly and all of a sudden you're shot up to the top of the hill and you go on your ride."
As you drop from the top of the hill your body goes into free fall.
This is when your body is accelerating towards the ground, pulled by gravity.
It feels like weightlessness and it's what makes your stomach flip.
The rollercoaster continues on, increasing and decreasing in speed as the track rises and falls.
This acceleration and deceleration is why you feel like you're stuck to, or coming out of, your seat.
The big thrill on rollercoasters is the loop.
During the loop there is a constant change in direction and acceleration.
Your body wants to continue on in a straight line but the track changes direction, applying a central force and pushing you round the loop.
The force in the loop makes you dizzy, but is what keeps you in your seat!
Without an engine, rollercoasters rely on electromagnetic force, free fall, acceleration and deceleration, and changes in direction to propel them.
These forces combine to create a thrilling ride that can make your body float, your heart race, and your stomach flip.