Law of conservation of energy:

Total energy is constant in any process. It may change in form or be transferred from one system to another, but the total remains the same.

Everyday Examples: Law of Conservation of Energy
The law of conservation of energy can be seen in these everyday examples of energy transference:

• Water can produce electricity. Water falls from the sky, converting potential energy to kinetic energy. This energy is then used to rotate the turbine of a generator to produce electricity. In this process, the potential energy of water in a dam can be turned into kinetic energy which can then become electric energy.
• When playing pool, the cue ball is shot at a stationary 8 ball. The cue ball has energy. When the cue ball hits the 8 ball, the energy transfers from the cue ball to the 8 ball, sending the 8 ball into motion. The cue ball loses energy because the energy it had has been transferred to the 8 ball, so the cue ball slows down.
• Kelly ran across the room and bumped into her brother, pushing him to the floor. The kinetic energy she possessed because of her movement was transferred to her brother, causing him to move.
• When a moving car hits a parked car and causes the parked car to move, energy is transferred from the moving car to the parked car.
• When playing the lawn game bocce ball, a small ball is thrown with the intention of hitting larger balls and causing them to move. When a larger ball moves because it was hit by the small ball, energy is transferred from the small ball to the larger one.
• When you push a book across the table, the energy from your moving arm is transferred from your body to the book, causing the book to move.
• A cat sitting on the highest branch of a tree has what is known as potential energy. If he falls off the branch and falls to the ground, his potential energy is now being converted into kinetic energy.
• When kicking a football that is sitting on the ground, energy is transferred from the kicker’s body to the ball, setting it in motion.
• Sam was rearranging furniture, and needed help to push the heavy sofa. His brother came over, and together they were able to lift the sofa onto sliders. This made it easy to push the sofa across the room. When Sam and his brother pushed the sofa and it slid across the wood floor, energy was transferred from the men to the piece of furniture.
• A fly ball hits a window in a house, shattering the glass. The energy from the ball was transferred to the glass, making it shatter into pieces and fly in various directions.
• Two football players collided on the field, and both went flying backwards. Energy was transferred from each player to the other, sending them in the opposite direction from which they had been running.
• Claire threw the ball and it hit her mother’s vase, knocking it over. Energy was transferred from the moving ball to the stationary vase, causing the vase to move.
• Fingers hitting piano keys transfer energy from the player’s hand to the keys.
• Billy hit the punching bag, transferring energy from his arm to the stationary bag.
• The dog ran in into the Christmas tree and knocked it over. Energy was transferred from the moving dog to the stationary tree, causing the tree to move.
• When the car hit the road sign, the sign fell over. Energy was transferred from the moving car to the stationary sign, causing the sign to move. No energy was lost in the transfer.
• Potential energy of oil or gas is changed into energy to heat a building.
• When a bowling ball knocks over pins that had been standing still, energy is transferred from the ball to the pins. No energy is lost.
• Beth hit the wall so hard that she put a hole in it. Energy was transferred from Beth’s body to the drywall, causing it to move.
• When the car hit the curb it broke apart. Energy from the moving car was transferred to the non-moving cement, causing it to move.

These law of conservation of energy examples show how commonplace this physics concept is in everyday life.
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