Kinetic Energy and Potential Energy: We all know that energy can neither be created nor destroyed; it changes its forms. Similarly, kinetic energy also transforms from one form to another. The motion required energy, and so did the stillness. The energy due to motion is called kinetic energy, and its opposite is potential energy. Let us know about kinetic energy in more detail through this concept explainer.
What is Kinetic Energy?
Kinetic energy is the energy of an object due to its motion. Any moving object, whether it's a car, a ball, or a molecule, has kinetic energy. This form of energy depends on the mass and velocity of the moving object.
Kinetic Energy Units
The standard unit of kinetic energy in the International System of Units (SI) is the joule (J). One joule is equal to one-kilogram meter squared per second squared (1J=1kg⋅m2/s2).
Kinetic Energy Examples
- A moving car: A car travelling at 60 km/h has kinetic energy due to its mass and velocity.
- A thrown baseball: The baseball has kinetic energy as it moves through the air.
- A running person: A person running has kinetic energy proportional to speed and mass.
Kinetic Energy Transformation
Kinetic energy can be transformed into other forms of energy, such as potential, thermal, or electrical energy, and vice versa. For example, when a car stops, its kinetic energy is converted into thermal energy due to friction in the brakes.
Kinetic Energy Formula
The kinetic energy (KE) of an object is calculated using the formula: KE=1/2mv2
where:
- m = mass of the object (kilograms)
- v = velocity of the object (meters per second)
Deriving Kinetic Energy Formula
Starting from the work-energy principle, the work done (W) to accelerate an object from rest to velocity v is given by: W=F⋅d
Using Newton's second law (F=ma) and the kinematic equation (v2=u2+2ad) where u=0
W=ma⋅v2/2a=1/2mv2
Thus, the kinetic energy (KE) is: KE=1/2mv2
Kinetic Energy Calculation
Example: Calculate the kinetic energy of a 70 kg person running at 5 m/s. KE=1/2mv2=1/2×70×52=1/2×70×25=875 J
The kinetic energy is 875 joules.
Why is Kinetic Energy a Scalar Quantity?
Kinetic energy is a scalar quantity because it only has magnitude and no direction. Unlike vectors, which have both magnitude and direction, scalars are described solely by their size.
Types of Kinetic Energy
Translational Kinetic Energy
- Description: Energy due to the linear motion of an object.
- Formula: KE=1/2mv2
Rotational Kinetic Energy
- Description: Energy due to the rotation of an object around an axis.
- Formula: KErot=1/2Iω2
- I = moment of inertia
- ω = angular velocity
Vibrational Kinetic Energy
- Description: Energy due to the vibrational motion of molecules.
- Example: Vibrations in a tuning fork or molecules in a solid.
Thermal Kinetic Energy
- Description: Energy due to the random motion of particles within a substance, contributing to its temperature.
- Example: The kinetic energy of molecules in boiling water.
Electrical Kinetic Energy
- Description: Energy due to the movement of electrons in an electric current.
- Example: The kinetic energy of electrons moving through a conductor.
Difference Between Kinetic Energy and Potential Energy
Let us understand the basic difference between kinetic and potential energy.
| Feature | Kinetic Energy | Potential Energy |
| Definition | The energy of an object due to its motion. | Energy stored in an object due to its position or state. |
| Formula | KE=1/2mv2 | PE=mgh (gravitational potential energy) |
| Dependency | Depends on the mass and velocity of the object. | Depends on the mass, height, and gravitational force (for gravitational potential energy). |
| Example | A moving car, a flying baseball, a running person. | A rock at the edge of a cliff, a compressed spring. |
| Type of Quantity | Scalar | Scalar |
| SI Unit | Joules (J) | Joules (J) |
| State of Object | Active (in motion) | Static (positioned or in a state of tension) |
| Conversion | Can be converted into potential energy and other forms of energy. | Can be converted into kinetic energy and other forms of energy. |
| Presence | Present in moving objects. | Present in objects with the potential to move or change state. |
References and Further Reading
You can refer to the reference material provided in the below mentioned links for better preparation and understanding scientific concepts.
- Books
NCERT Class 10 Science Textbook PDF
NCERT Class 12 Physics Textbook PDF
- Articles
Magnetic effects of Electric Current
- Online Resources
CBSE Class 10 Science Video Tutorials
CBSE Class 12 Physics Video Tutorials
Also Check:
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