Difference between Kinetic Energy and Potential Energy

Energy exists in various forms, with kinetic energy and potential energy being two of the most fundamental types. While kinetic energy is the energy of motion possessed by a moving object, potential energy is the stored energy an object has due to its position or state. These energies can transform into one another. Both are forms of mechanical energy, and they play an important role in everyday activities and natural processes.

Here, we’ll explore the key distinctions between kinetic and potential energy, including their definitions, formulas, and units of measurement, and we will also examine their examples.

Kinetic Energy 

Kinetic energy is the energy an object has because of its motion. It depends on both the mass of the object and how fast it is moving. An object that is heavier or moving faster will have more kinetic energy.

An object that is heavier or moving faster will have more kinetic energy. This type of energy is present in everyday actions; like a rolling ball, a moving car, or a flying airplane .

Formula of Kinetic energy,

K.E. = 1/2mv²

Where, m = mass (kg) and v = velocity (m/s).

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Potential Energy 

Potential energy is the stored energy in an object or system based on its position, condition, or arrangement. It represents the energy an object holds that can be released or transformed into other forms, such as kinetic energy, when its position or state changes. For example, a stretched rubber band or an object held at a height has potential energy that can be converted into motion.

Formula of Gravitational potential energy ,

W = m × g × h = m.g.h 

Where, m = mass (kg) 

g = acceleration due to gravitational field (9.8 m/s²) 

h = height (m) 

Elastic potential energy can be found using the formula,

U = 1/2kx²

Where k = spring force constant 

x = stretch length (m) 

Unit of energy = Joule (J).

Read More, Potential energy

Here below some differences between kinetic Energy and Potential Energy :

Sample Questions

Question 1: Kinetic energy can be negative? Explain.

Answer:

The general formula of kinetic energy is 1/2 mv². According to this, as mass never be negative and here 'v' speed is the square and always give non-negative term so kinetic energy cannot be negative.

Question 2: In a running competition, a boy whose weight is 20 Kg is running at a speed of 2m/s. Calculate the kinetic energy of the boy.

Solution:

Given: mass(m) = 20Kg
Velocity (v) = 2m/s
Kinetic Energy (K.E) = 1/2 mv²
K.E = 1/2 × 20 × (2)²
K.E = 40 Kgms^-2.

Question 3: A box of mass 30 Kg is stored at a height of 10m. Calculate the potential energy of the box. Consider the value of acceleration due to gravity(g) = 10m/s².

Solution: 

Given: Mass(m) = 30Kg
Height(h) =10m and g = 10m/s² .
Potential Energy = m.g.h
P.E = 30 × 10 × 10
P.E = 3000 Kgm² s^-2 .

Question 4: State whether sound energy is Kinetic or potential?

Answer:

Sound is what most of us perceive as a kinetic form, but it can be considered as two forms of energy at the same time. The sound energy in the air produced by longitudinal waves that produce the movement of gas molecules is kinetic. Solids and liquids, which transmit sound farther than air, have both Kinetic and potential energy.

Question 5: Calculate the height of an object whose potential energy is 2000 Kgm²s^-2 and mass is 20 Kg. Consider the value of acceleration due to gravity(g) = 10m/s².

Solution: 

Given: P.E = 2000 Km²s^-2
Height(h) = 10 m  and g = 10 m/s
Potential Energy = m.g.h
2000 = 20 × 10 × h
h = 2000/20 × 10
h = 10 m.

Question 6: An object is moving with a velocity of 4m/s having a mass of 15 Kg. Calculate the kinetic energy of that object.

Solution:

Given: Mass (m) = 15 Kg
Velocity (v) = 4m/s.
Kinetic energy = 1/2 mv²
K.E = 1/2 × 15 × (4)²
K.E = 120 J.