Question

Define kinetic energy with example.

Answer 1

Hint : In this question, we have to define kinetic energy. We define this using this formula$K.E=\dfrac{1}{2}m{{v}^{2}}$. This formula states the concept of kinetic energy. So we are using this formula to define the kinetic energy.

Complete step by step answer: Kinetic energy is the energy that is possessed by a body by its motion. We have to exert force to accelerate a particle & to exert force we require to do work. When the work is done on the particle, energy is transferred & the particle then travels with a new persistent speed. The energy that is transferred is called kinetic energy & this kinetic energy depends on the speed & mass achieved.
Units of kinetic energy are:
The SI unit is Joule that is equal to $1kg.{{m}^{2}}.{{s}^{-2}}.$
The CGS unit is erg.
Deriving equation of kinetic energy:
The equation of kinetic energy can be produced by the basic method of computing work $W$ that is done by a force $F$. If a body of mass $m$is pushed for a distance $d$ on a surface by exerting a force that is parallel to it, then work done will be:
$W=F.d$
We know that$F=ma$. Then the equation will be,
$W=m.a.d$
In this equation, acceleration can be substituted by the initial velocity${{v}_{i}}$, final velocity ${{v}_{f}}$ & distance. This can be obtained from the equations of kinematic motion.
$W=m.a.d$
Here we substitute the value of$a$,
$W=m.d.\dfrac{{{v}^{2}}_{f}-{{v}^{2}}_{i}}{2d}$
After solving this equation further we get,
$W=m.\dfrac{{{v}^{2}}_{f}-{{v}^{2}}_{i}}{2}$
We can also write this equation as,
$W=\dfrac{1}{2}.m.{{v}^{2}}_{f}-\dfrac{1}{2}.m.{{v}^{2}}_{i}$
Further simplifying the equation, we get
$K.E=\dfrac{1}{2}m{{v}^{2}}$
We can say that the overall work that is done on a body is equal to the change in kinetic energy. This statement can be equated as follows:
${{W}_{net}}=\Delta K$
This equation is called a work-energy theorem.
Examples of kinetic energy:
A truck moving down the road will have more kinetic energy as compared to a car as the mass of the truck is more than that of a car.
An insect when flying contains a small amount of kinetic energy as its velocity & mass are relatively small.

Note: To understand this question we have to study kinetic energy. In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. After understanding the concept of kinetic energy we can easily solve these types of questions.