Law of Conservation of Energy is energy that is not lost or created only transferred from one form to another.

There are two types of energy. Gravitational Potential Energy and Kinetic Energy. Gravitational Potential Energy depends on the objects height, mass, and the acceleration of gravity. The Kinetic Energy of an object depends on one-half times the mass and velocity squared. Remember that gravitational potential is the energy stored in an object and that kinetic energy is what an object posses when it is moving.

Conservation of Energy​

Take this picture for example. The  Gravitational Potential energy is highest due to its height where the object stores the most energy. This type of gravitational potential energy will then be transferred into kinetic energy as the roller coaster starts accelerating downwards.When the roller coaster reaches the bottom of the hill that's the spot where it has reached its maximum kinetic energy. Keep in mind that the roller coaster keeps on transferring kinetic and gravitational potential energy back and forth, but the total energy stays the same. 

In this Phets simulation,  you can see that the skater is heading down the slope. The picture froze at the time where the kinetic energy is starting to build up and the potential energy was about to decrease. The larger the skater is the slower he moves through this simulation. Furthermore all throughout this simulation the total energy does not change because of the definition of law of conservation of energy where energy can't be created or destroyed just transferred. For more information click on the picture !!!Fun stuff happens ;)

​Ever wondered why roller coasters can't go on forever? Well  you have come to the right place. I will answer all your questions. Friction is the reason why roller coasters rides come to a stop. Friction is caused by rubbing of the car wheels on the track and also the rubbing of air, sometimes water :) against cars.  Friction is also the reason why roller coasters never regain maximum height after initial hill unless 2nd chain lift somewhere on the track. In addition to friction have you ever wondered how you were able to survive a loop, like the picture on the left? Well it is due to the roller coaster's critical velocity. If the car is not moving fast enough at top, it will FALL! Cars ONLY make loop if there is enough speed at the top. The picture shown at the left is referred to as a   clothoid or a teardrop shape loop. Because of many neck injuries a circular loop was abandoned until 6 flags brought it back with some major improvements. They decided to make the loop widest at the bottom, reducing the force on riders when cars move fastest and smallest at top. ​

Inception :)

This contraption is called Newton's Cradle.If you pull a ball up and out and then release it, it falls back and collides with the others and makes a clicking noise. You would expect all 4 balls to move don't you? Don't be fooled. Only the ball at the opposite end will move and this cycle will keep on repeating until it eventually slows down and stops. Kinetic and Gravitational potential energy and law of conservation are the 3 physics principles that is taking place. The gravitational potential energy of the first ball gets transferred into kinetic energy and hits the rest of  the four balls. The only one that absorbed that energy was the ball at the end and caused the ball to leave the others.