Relation between Kinetic Energy and Momentum

Kinetic energy and momentum are the two terms related to an object in motion. In this article, we will explore the relation between kinetic energy and momentum.

Table of Contents

Kinetic Energy

The kinetic energy of an object is the energy associated with the object which is under motion. It is defined as “the energy required by a body to accelerate from rest to stated velocity.” It is a scalar quantity.

Kinetic Energy Formula

Mathematically expressed as-

\(\begin{array}{l}K.E=\frac{1}{2}mv^{2}\end{array} \)

Where,

m is the mass of the object measured in kg.

v is the velocity of the object measured in m/s.

Read More: Kinetic Energy

Kinetic Energy Unit

The SI unit of Kinetic Energy is Joules.

Momentum

The momentum of an object is the virtue of its mass. It is defined as the product of mass and velocity. It is a vector quantity.

Momentum Formula

The momentum of a moving object can be mathematically expressed as –

\(\begin{array}{l}p=mv\end{array} \)

Where,

  • p is the momentum.
  • m is the mass of the object measured using kg.
  • v is the velocity of an object measured using m/s.

Momentum Unit

The SI unit of Momentum is kg.m/s.

Watch the video and learn more about energy and momentum

Relation between Momentum and Kinetic Energy

Kinetic energy and momentum of a moving body can be mathematically related as follows-

Consider the formula of kinetic energy-

\(\begin{array}{l}K.E=\frac{1}{2}mv^{2}\end{array} \)

Multiply and divide R.H.S by m,

\(\begin{array}{l}\Rightarrow K.E=\frac{1}{2}mv^{2}\times \frac{m}{m}\end{array} \)
\(\begin{array}{l}=\frac{m^{2}v^{2}}{2m}\end{array} \)
\(\begin{array}{l}=\frac{\left ( mv \right )^{2}}{2m}\end{array} \)

We know that

\(\begin{array}{l}p=mv\end{array} \)
. Substituting for mv in the above equation we get-

\(\begin{array}{l}K.E=\frac{p^{2}}{2m}\end{array} \)

The above equation gives the relation between kinetic energy and momentum of the object which is under motion.

If the Momentum(p) is constant
\(\begin{array}{l}K.E\propto \frac{1}{m}\end{array} \)
If Kinetic Energy(K.E) is constant
\(\begin{array}{l}p\propto \sqrt{m}\end{array} \)
If mass(m) is constant
\(\begin{array}{l}p\propto \sqrt{K.E}\end{array} \)

Hope you have understood the relation between Kinetic energy and momentum of a moving object.

Physics Related Topics:

Newton’s Second Law of Motion
Impulse Units
Acceleration
Momentum

Frequently Asked Questions – FAQs

Q1

What is kinetic energy?

The kinetic energy of an object is the energy associated with the object which is under motion. It is defined as “the energy required by a body to accelerate from rest to stated velocity.” It is a vector quantity.
Q2

Define momentum.

The momentum of an object is the virtue of its mass. It is defined as the product of mass and velocity. It is a vector quantity.
Q3

State the law of conservation of momentum.

The law of conservation of momentum states that in an isolated system the total momentum of two or more bodies acting upon each other remains constant unless an external force is applied. Therefore, momentum can neither be created nor destroyed.
Q4

The law of conservation of momentum is based on which law of motion?

The law of conservation of momentum is based on Newton’s third law of motion which states that every force has a reciprocating equal and opposite force.
Q5

What is the formula for the law of conservation of momentum?

The momentum observation principle can be mathematically represented as:
m1u1 + m2u2 = m1v1 + m2v2
In the equation, m1 and m2 are masses of the bodies, u1 and u2 are the initial velocities of the body.
v1 and v2 are the final velocities of the bodies.

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