Kinetic energy can be defined as the energy which is present in every moving object. We can simply say that kinetic energy is the energy because of motion. Kinetic energy can be further classified into various types based on the type of motion of the objects. For example, rotational kinetic energy is the energy possessed by a body which is moving in circles, e.g. planets revolving around the sun have rotational kinetic energy; vibrational kinetic energy is the energy possessed by an object due to vibration, e.g. vibrating phone has a vibrational kinetic energy; translational kinetic energy is the energy possessed by an object moving from one point to another. Translational kinetic energy can be easily observed in our everyday life.
Kinetic energy depends upon two things, i.e. mass (m) and velocity (v) as the formula of kinetic energy depicts;
K= ½ mv^2
where ‘m’ is the mass of the object that is in motion and ‘v’ is the velocity. Therefore, by the above formula, we can say that kinetic energy is directly proportional to the mass and square of the speed of the object in motion. By keeping this formula in mind, let us take a few examples where we observe kinetic energy in our day-to-day life.
1. Hydropower Plants
Hydropower plants are places where the generation of electricity takes place with the help of water. When the water which is moving, and therefore, possessing some kinetic energy, hits the turbine present in the dam, the kinetic energy of the water gets converted into mechanical energy. This mechanical energy moves the turbines and, then, ultimately leads to the production of electrical energy.
2. Wind Mills
Windmills form one of the good examples of applications of kinetic energy. In a windmill, when the wind (air in motion) hits the blades, it causes the rotation which ultimately leads to the generation of electricity. Here, the moving air has kinetic energy which causes the rotation of blades, and therefore, in this example too, the kinetic energy is converted into mechanical energy.
3. Moving Car
Cars moving on roads possess some amount of kinetic energy. This is because they have some mass and velocity. Recalling the formula of kinetic energy, we now know that while comparing a truck and car moving on a road with the same velocity, we will come to the conclusion that the truck will have higher kinetic energy because of its large size. Since kinetic energy is directly proportional to the mass of the moving object, therefore, a truck will have more kinetic energy than a car.
4. Bullet From a Gun
A bullet fired from a gun has very high kinetic energy, and, so, it can easily penetrate any object. This is because of a large amount of velocity possessed by the bullet. Although the mass of the bullet is less, its high speed renders double the amount of kinetic energy.
5. Flying Airplane
A flying aeroplane has a very high amount of kinetic energy because not only does it has a large mass, but also a very high velocity. Both these figures result in heightened kinetic energy of the aeroplane when it is flying. This is the reason why aeroplanes are able to fly high.
6. Walking & Running
When walking or running, we possess some amount of kinetic energy. This is why we feel comparatively warm while running or after walking some distance. Sweat is the result of the heat produced by our body due to running. While walking or running, there is a conversion of chemical energy into kinetic energy.
The moving bicycles possess kinetic energy. The mechanism behind it is that when we start pedalling, we are converting our energy into the mechanical form, which is initially the potential energy and ultimately is converted into kinetic energy due to the motion of the wheels. More the velocity more will be the kinetic energy. In order to stop the bicycle, we need to apply the brakes, opposite to the force, in order to decelerate the bike and get back to zero energy.
Roller coasters are fun to ride, but ever given a thought about your wagon during a free fall? Well, when the wagon of a roller coaster is at the top, it has zero kinetic energy because the wagon is at rest. But when it is allowed to do a free fall, with the gradual increase in the speed of the wagon, a gradual increase in the kinetic energy also takes place. If a number of people are sitting in the wagon, it will increase the mass and, hence, the kinetic energy, provided that the speed remains constant.
9. Cricket Ball
When a bowler has a cricket ball in his hand, the kinetic energy of that ball is zero because it is at rest. But as soon as the bowler throws the ball towards the batsman, it begins to accumulate kinetic energy from to its mass and the speed at which it is thrown. This is the reason why batsmen always wear safety gears so that they do not get injured as the ball possesses a high amount of kinetic energy.
Similar to the case of a bicycle, when a person riding a skateboard is at rest, the kinetic energy will be zero. As the skateboard moves, the kinetic energy gradually starts increasing. Similarly, when the weight of a skateboard’s rider is coupled to the high speed of the board, a large amount of kinetic energy is generated.
11. Dropping a Glass on Floor
What happens when we accidentally drop a glass on the floor? Initially, at the highest point, it possesses potential energy only, but as the gravity works and the speed is accelerated, the mass of the glass and velocity become responsible for the gradual increase in the kinetic energy. At the lowest point when the glass is about to hit the ground, the kinetic energy becomes maximum while the potential energy becomes minimum or negligible. Finally, when the glass hits the ground and breaks, the kinetic energy is released.
12. A Bus Moving on the Hill
A bus, at the highest point of the hill, will have more potential energy due to the height with almost no coefficient of kinetic energy. As the bus moves down the hill with some velocity, the potential energy due to the height will decrease and the kinetic energy will increase. There will come a point where the value of both, the kinetic as well as potential energy, will become the same. When the bus will reach the bottom of the hill, the kinetic energy will become maximum; as long as it is moving at a constant velocity the potential energy will become zero.
13. Meteor Shower
Although this example does not form a day-to-day example of kinetic energy, still it is a very interesting phenomenon that takes place in the solar system. You might be aware of the fact that meteoroids are scattered in our solar system. Whenever any meteoroid comes close enough to the earth’s atmosphere, it gets attracted by the gravity. As a result, it starts falling freely from the sky at a high speed. At that time, the kinetic energy of the meteorite is quite high because of its enormous size and weight. When it hits the surface of the earth with such a large amount of kinetic energy, explosions occur. Also, this is the reason for the presence of impact craters on the earth’s surface.