Energy! Have you ever had trouble finishing your workday? felt too tired to think clearly? had trouble getting out of bed? You were probably suffering from a lack of energy.
Every living thing needs and uses energy to complete its life’s actions. Energy not only gives us the power to work, it also allows us to hear our favorite music, surf the Pacific Ocean, and warm ourselves on a cold winter night. Physics is the science of energy. Physicists are concerned with how energy is produced, in what forms it can come, and how to make energy creation and consumption more efficient. How important is this science?
Well, the world’s population is increasing faster than ever. Improvements in medicine and health have not only extended peoples’ life spans, but they have also lowered infant mortality, especially compared to just a hundred years ago. Our standard of living across the world has been rising likewise. More and more products consume some type of energy, from electricity, to gasoline, to batteries. Therefore, the need for energy has increased to an all-time high.
Often, it is the physical scientists who have the task of finding the energy we need to continue to grow. Physicists have been responsible for inventions making us more efficient, from the microwave, to incredible feats such as landing on both the Moon and Mars. In general, physicists often become involved in projects that have practical applications.
One of the most pressing challenges for physicists today is the possibility of an energy shortage. Imagine how your life would be affected if you could not buy gasoline. Imagine if you could only use electricity for 2 hours a day, or take a hot shower only once a week. Where can we get the new sources of energy we will soon need to meet the world’s demands? More importantly, are there any renewable sources, in other words, energy sources that will never run out?
Law of Conservation of Energy
First of all, what is energy? Energy is defined as the ability to do work. Work is the idea of moving something, by using a force, over a distance. An object must have energy to be able to move something, maybe even itself, over a distance. That is why energy is crucial. Nothing would work without it!
When you turn on an electric stove, electricity is used to heat up the burner. This heat can then be used to cook your food. A physicist would view this as a change in forms of energy, from electrical energy to heat energy; it is this change that is the foundation of a law in physics, the Law of Conservation of Energy. A law is a statement or observation that always seems to be true and has stood up to scientific observation and testing.
Two Types of Energy
Have you ever been on a roller coaster? A roller coaster is a great example of the laws of physics. When you first climb in and secure yourself, the coaster does not have any energy. Yet, the coaster must climb the first large hill. Traditional coasters use a chain or cable to slowly pull it to the top of the first hill, because coasters are powered by gravity. Gravity is the downward force pulling every object toward the Earth. Once at the top of the hill, the coaster is filled with potential or stored energy. The mechanical energy used to pull the coaster up the hill, now has been transformed into a different type of energy, the energy of position. The higher an object is, the more potential energy it has. This is when gravity causes the coaster to plummet down the hill. All of the coaster’s potential energy is then transformed into kinetic energy, or the energy of motion.
Potential Energy is the energy of position. A resting object’s position determines how much potential energy it holds. As a coaster climbs, it will gather potential energy.
Kinetic Energy is the energy of motion and speed. The more speed it has, the more kinetic energy it has.
At the top of each hill, the coaster’s kinetic energy is 0. At the bottom of each dip, the coaster’s potential energy is 0. As long as the coaster is moving up and down the hills, the type of energy will keep changing. Notice that each successive hill will be shorter and shorter. This is because of the forces working against it. Some of its energy is lost as heat and sound. Air resistance also slows the coaster down. Gravity also forces the coaster downward, but with all of these forces working against it, what keeps the coaster’s momentum going? That will be answered in a later section.
Now, if energy is the ability to do work and work is using a force to move an object over a distance, can you see how a roller coaster can demonstrate these principles? Work, in this example, is moving the coaster along the tracks. The force to do the work consists of the initial mechanical force of the chain pulling it up the hill followed by, the force of gravity pushing it down the hill. The distance is the length the coaster travels, and it takes energy to do this work.
Amusement rides in the future are looking for other ways to propel and to stop a ride smoothly and efficiently. Southern California’s Magic Mountain showcases a ride called Superman the Escape. This ride is unique because it uses state of the art “linear synchronous motors,” which uses the fundamentals of magnetism to propel it up a steep 415 foot incline at speeds of 100 mph, and it does this in only 7 seconds! Then, the force of gravity causes it to free-fall back down the incline. This makes it the tallest and fastest thrill ride in the US.