What is Energy?
Energy is the capacity to do work in physics. It exists in potential, kinetic, thermal, electrical, chemical, nuclear, or other forms. You can connect with the best online learning platform Vedantu, to get a complete understanding of the topics related to the chapter Energy and download FREE PDF Potential and Kinetic Energy - Different Types, Formula, Solved Numericals, etc.
Potential Energy
Potential Energy definition states that “It is the energy stored that depends on the relative location of the different parts of the system”. In systems with parts that exert forces on each other of a magnitude depending on the configuration or relative position of the parts, Potential Energy arises.
When compressed or extended, spring has more Potential Energy. A steel ball after dropping to Earth has less Potential Energy compared to when lifted above the ground. Potential Energy is capable of doing more work in an elevated role. Potential Energy is a system property and not of an individual body or particle; for example, the system consisting of Earth and the raised ball has more Potential Energy as the two are separated further.
The Potential Energy of an object depends only on its original and final configurations. It is independent of the direction traveled by the objects. If the initial position of the ball is ground level and the final position is 10 m above the ground, in this case of the steel ball and the Earth, the Potential Energy is the same, regardless of how or by what route the ball was lifted. The value of Potential Energy is arbitrary and is proportional to the reference point selection. In the above example, if the initial location was the bottom of a 10 m deep pit, the device would have twice as much Potential Energy.
Different Types of Potential Energy
Electrical Potential Energy is the energy stored between the plates of a charged capacitor.
Chemical energy, the ability of a substance to work or to produce heat from a change in structure, may be considered as Potential Energy arising from the reciprocal forces between its molecules and atoms.
Nuclear energy is a form of Potential Energy as well.
Gravitational Potential Energy
The Potential Energy that a massive object has another massive object due to gravity is Gravitational Potential Energy. When the objects fall towards each other, it is the Potential Energy associated with the gravitational field that is released.
By multiplying the weight of an object by its distance above the reference point, Gravitational Potential Energy near the Earth's surface can be measured.
Inbound structures, such as atoms, where electrons are retained by the electrical force of attraction to nuclei, the zero reference for Potential Energy is such that the distance from the nucleus is not measurable by the electrical force. Bound electrons have negative Potential Energy in this case, and those so far away have zero Potential Energy.
Potential Energy Formula
The Gravitational Potential Energy formula relies on the force that acts on the two objects. The formula for the Gravitational Potential Energy is,
P.E. = m*g*h
Where m is the mass in kilograms,
g is the acceleration due to gravity(9.8 m/s2 at the earth's surface) and
h is the height in meters.
The SI unit of measurement of Potential Energy is kg. m2/s2 or Joule(J).
Some examples of Potential Energy include:
Compressed or extended spring.
A ball raised to some height.
Stored water in the Dam.
A car parked on the hilltop.
An arrow about to be shot.
Kinetic Energy
Kinetic Energy is the form of energy in which the object or a particle is said to be in motion. If the work that transfers energy is done on an object by applying a net force, the object speeds up and thus gains Kinetic Energy.
Kinetic Energy is a property of a moving object or particle which depends not only on its movement but also on its mass. Translation, rotation around an axis, vibration, or some combination of motions can be the form of Kinetic Energy.
Kinetic Energy Formula
Kinetic Energy is directly proportional to the object's mass and its velocity square, which is K.E. = 1/2*m*v²
Where m is the mass in kilograms,
v is the velocity in m/s.
The SI unit of measurement of Kinetic Energy is the same as Potential Energy which is kg. m2/s2 or Joule(J).
The Relation Between Potential Energy and Kinetic Energy
Kinetic Energy is nothing but a form of converted Potential Energy. Potential Energy can be transformed into the energy of motion such as Kinetic Energy and in turn into other forms, such as electric energy. Thus, through turbines that transform electric generators, water behind a dam flows to lower levels, generating electric energy plus some unusable heat energy resulting from turbulence and friction.
Potential Energy and Kinetic Energy are a form of mechanical energy so that the total energy in gravitational systems can be calculated as a constant.
Some examples of Kinetic Energy include:
Windmill.
Moving vehicle.
Running and Walking.
Bullet fired from a gun.
An arrow shot from a bow.
Cycling.
Solved Numerical on Potential and Kinetic Energy
1. In a running race competition, a student who is weighing 40 Kg is running at 4m/s. Calculate the Kinetic Energy of the student.
Ans: It is given that the weight/mass of the student, m = 40 Kg.
The velocity of a student, v = 4m/s.
Kinetic Energy is given by the formula, K.E.=1/2*m*v²
Substituting the values we get, K.E.= 1/2 * 40 * 4*4 = 320 kg. m2/s2.
Therefore the Kinetic Energy of the student is 320 kg. m2/s2.
2. A water tank of mass 50 Kg is stored at a height of 10m. Calculate the Potential Energy of the tank. Consider the value of acceleration due to gravity(g) = 10 m/s2.
Ans: Given the mass of the tank, m = 50 Kg.
Height = 10m and g = 10 m/s2.
Potential Energy formula is given as P.E. = m*g*h.
Substituting the values we get P.E. = 50*10*10= 5000 kg. m2/s2.
Therefore the Potential Energy of the tank is 5000 kg. m2/s2.
FAQs on Potential and Kinetic Energy
1. What is potential energy and what are its main types?
Potential energy is the stored energy an object has due to its position, state, or configuration. It is the energy that has the 'potential' to be converted into other forms of energy, like kinetic energy. The primary types include:
- Gravitational Potential Energy: Energy stored in an object due to its vertical position or height in a gravitational field. For example, a book on a high shelf.
- Elastic Potential Energy: Energy stored in an elastic object when it is stretched or compressed, like a drawn bow or a compressed spring.
- Chemical Potential Energy: Energy stored within the chemical bonds of a substance, which is released during a chemical reaction.
2. What is kinetic energy and how is it calculated?
Kinetic energy is the energy an object possesses due to its motion. Any object that is moving has kinetic energy. It is directly proportional to the mass of the object and the square of its velocity. The formula to calculate kinetic energy is:
K.E. = ½ * m * v²
Where:
- K.E. is the kinetic energy in Joules (J).
- m is the mass of the object in kilograms (kg).
- v is the velocity of the object in meters per second (m/s).
3. What is the fundamental difference between potential and kinetic energy?
The fundamental difference lies in their nature: potential energy is stored energy based on an object's position or state, while kinetic energy is the energy of motion. An object can have potential energy while being perfectly still (e.g., a rock at the top of a hill), but it must be moving to have kinetic energy. Potential energy can be converted into kinetic energy, such as when the rock starts to roll down the hill.
4. Can you provide some real-world examples of potential and kinetic energy?
Certainly. Here are examples for both:
- Examples of Potential Energy: A car parked at the top of a hill, water held back by a dam, a stretched rubber band, and a compressed spring.
- Examples of Kinetic Energy: A moving car, a flowing river, a flying arrow, and a spinning windmill.
5. How are potential and kinetic energy related through the law of conservation of energy?
Potential and kinetic energy are two forms of mechanical energy. According to the law of conservation of energy, in an isolated system where only conservative forces (like gravity) act, the total mechanical energy (the sum of potential and kinetic energy) remains constant. This means that energy is not lost but is continuously transformed between potential and kinetic forms. For instance, as a roller coaster goes down a hill, its potential energy converts into kinetic energy, increasing its speed. As it goes up the next hill, kinetic energy is converted back into potential energy, and it slows down.
6. Can an object possess both potential and kinetic energy at the same time?
Yes, absolutely. An object can have both forms of energy simultaneously. A common example is a flying bird or airplane. It has kinetic energy because it is moving, and it has gravitational potential energy because it is at a certain height above the ground. Another example is a satellite orbiting the Earth; it has kinetic energy due to its orbital speed and potential energy due to its position in Earth's gravitational field.
7. Why is potential energy often described as a property of a system, not just a single object?
Potential energy arises from the interaction between two or more objects. For example, gravitational potential energy doesn't belong to a ball alone; it belongs to the system of the ball and the Earth. The energy exists because of the gravitational force between them and their separation distance. If the Earth weren't there, the ball wouldn't have gravitational potential energy. Similarly, elastic potential energy exists in a spring system only when an external force deforms it, involving the interaction between the force and the spring's internal structure.
8. What is the formula for calculating gravitational potential energy?
The formula for calculating gravitational potential energy for an object near the Earth's surface is:
P.E. = m * g * h
Where:
- P.E. is the potential energy in Joules (J).
- m is the mass of the object in kilograms (kg).
- g is the acceleration due to gravity (approximately 9.8 m/s² on Earth).
- h is the height of the object above a reference point in meters (m).
