Potential energy is the resting form of energy present in any object. It can also be defined as the energy which is stored in an object due to its position, state, or composition. Potential energy can be of various types like electric potential energy– potential energy in an object due to its charge; gravitational potential energy– potential energy in an object when it is held vertically at some height; elastic potential energy– potential energy in those objects that can be compressed and stretched; chemical potential energy– potential energy stored in the chemical bonds of a substance.
Let us take the example of gravitational potential energy. As already discussed, an object will have gravitational potential energy if it is held vertically at some height. Or we can simply say that energy present in an object due to its height is called gravitational potential energy. When an object is present at some height, earth’s gravitational force acts on that object to attract it to the earth’s surface, therefore, it is called gravitational potential energy.
Gravitational potential energy in an object can be calculated as-
P.E = mgh
- ‘m’ is the weight of the object
- ‘g’ is the gravitational force applied by the earth i.e. 9.8 m/s^2
- ‘h’ is the height at which the object is held.
Therefore, we can say that gravitational potential energy is directly proportional to the weight of the object and height at which it is placed. More the weight of the object and more the height at which it is held, more will be the gravitational potential energy. The potential energy of a system of particles only depends upon the initial and final configuration. It is independent of the path followed by particle. For example; if an object has an initial position at the ground level and final position at some height ‘h,’ then, the potential energy will be independent of the path followed by that object to reach the height ‘h.’ So, the path can be zigzag or a straight line; as long as the height remains constant, the potential energy will remain the same for different paths.
By keeping in mind all the above information about the potential energy, let us now look at some examples of potential energy from everyday life.
Pendulums are the structures in which weight is suspended from a pivot so that they could easily swing; for example, the pendulum clocks. If a pendulum is held at one end, it has maximum potential energy at that time due to its position. But as we leave the bob, this potential energy is converted into kinetic energy. When the bob of the pendulum will reach the other end, before coming back by the same path, it will stop for a second at the highest point. At this resting stage of 1-2 seconds, the kinetic energy will be converted into potential energy. This process will be repeated again and again until the pendulum halts. The change in the energy will be similar to the diagram below-
As already discussed, elastic potential energy is a form of potential energy which is present in those objects that can be stretched and compressed; for example, a spring. When a spring is compressed or stretched, it gains some amount of potential energy called elastic potential energy whereas the energy that is required to compress the spring is called the kinetic energy. When a compressed spring is released, the stored potential energy of the compressed spring will again get converted into kinetic energy.
3. Bow & Arrow
Do you know that working of a bow and arrow employs the first law of thermodynamics which says that ‘energy can neither be created nor be destroyed; it can only be transferred from one form to another’? When an archer pulls back the bowstring, some amount of elastic potential energy is gained by the flexible limbs of the bow. The more an archer pulls back, the more potential energy will be gained by the limbs of the bow due to stretching. When the bowstring is released, the arrow moves forward very quickly. What happens here is that the potential energy that is gained by the bow due to stretching is being quickly transferred to the arrow in the form of kinetic energy, and so, it moves forward.
4. Rock At Cliff’s Edge
A rock on the edge of a cliff possesses potential energy. The potential energy in that rock will be due to its position. As we already know, the energy stored in an object due to its height is known as gravitational potential energy; therefore, we can say that the energy present in the rock will be gravitational potential energy. And likewise, if someone pushes that rock down the cliff, the same potential energy will then be converted into kinetic energy. So, the next time you are on your trip to the mountains and see a rock resting on the edge of a cliff remember that it has some energy stored in it in the form of gravitational potential energy.
5. Food We Eat
Ever thought about how we are able to walk, run, or do any work which requires a lot of energy? Where does this energy in our body to do all the work comes from? As we know that work done requires energy and, we, humans obtain our energy from the food we eat. As explained earlier, there is a type of potential energy present in substance that is called chemical kinetic energy. It is the energy that is stored in the chemical bonds of a substance. The food that we eat has some stored chemical potential energy. When food reaches our stomach, the same chemical potential energy is converted into the energy that our body utilises. We can say that everything that is made up of atoms has potential energy. Interestingly if we take two pieces of meats, a hot and a cold that weigh the same and compare them, we will find that the hot meat will have more energy compared to the cold meat because the former has some amount of additional thermal energy; however, the amount of potential energy will remain the same.
6. Water In Dams & Reservoirs
The water that is held in dam reservoirs for various purposes like generating electricity in hydropower plants, irrigation, prevention of flood, human consumption, industrial use etc, possesses some amount of potential energy. Since the water held in reservoirs is at rest and is prohibited from flowing, the energy present in it will be called potential energy because we know that potential energy is the type of energy present in objects at rest. When the gates of a dam open, this water, which was initially at rest, will be instantly put into motion and the stored potential energy in water will be converted into kinetic energy.
Have you ever seen the snow filled mountains that look so peaceful? When fresh snowfall occurs, the snow starts packing on the mountains. The snow which is at rest has some amount of potential energy in it. Since these mountains are present on some height, this potential energy can be classified as gravitational potential energy. When snowfall occurs, this packed cover of snow breaks which results in a snow avalanche. What happens in snow avalanches is that because of a break in the snow, the potential energy gets converted into the kinetic energy. Hence, snow starts moving down the mountain.
Before a bullet is fired from the gun, it is at rest. As we now know that the energy present in an object which is held at rest is called the potential energy. Therefore, we can say that the resting bullets inside the gun contain some amount of energy which is known as potential energy. And, as soon as, the bullets are fired, the potential energy will be converted into kinetic energy.
When a wagon is held at the top of a rollercoaster just before it is allowed to do a free fall, it contains some amount of potential energy. At the highest point of the rollercoaster, the wagon is held still for few seconds, the energy contained in the cart due to height and the weight of the people sitting in the wagon is called as gravitational potential energy. More the number of people riding the wagon more will be the gravitational potential energy. When the wagon slides further on the track, the stored potential energy is converted into the kinetic energy.
10. Rubber Band
When we stretch a rubber band, it stores some amount of potential energy inside it. Now, we can easily say that a stretched rubber band will have elastic potential energy stored inside. As soon as the stretched band is set free, it quickly returns to its original shape and the elastic potential energy gets converted into the kinetic energy.
11. Wrecking Ball
Wreaking ball is similar to a pendulum. When a crane swings a wrecking ball up to a certain height, it starts gaining some potential energy. Just like the case of a pendulum, here, also, the potential energy is converted into the kinetic energy which is used to crash the buildings.
Before diving into the water, swimmers always stand on the diving board and stretch. While the swimmers are standing on the diving board, they have some amount of gravitational potential energy. As soon as they dive into the water, this gravitational potential energy is converted into the kinetic energy. This is the reason why the swimmers take a jump while diving so as to obtain a maximum amount of gravitational potential energy which will be converted into the kinetic energy. More the kinetic energy, easier it will be to cut through the viscosity of the water in the pool.