Content Curator
Kinetic Energy is the energy that an object possesses due to its motion. There is a definite requirement for forces that need to be applied when an object is set to acceleration.
The energy of a body is its capacity of doing work. There are many forms of energy like heat energy, sound energy, nuclear energy, mechanical energy, and electrical energy.
- Kinetic energy is a type of mechanical energy.
- The energy gained during its acceleration is kept the same unless its speed changes.
- The activities like walking, jumping, throwing, and falling are examples of kinetic energy.
- It depends on the mass and speed achieved.
- Kinetic energy is a scalar quantity, and it is described in terms of magnitude alone.
Key Terms: Kinetic Energy, Potential Energy, Kinetic energy units, Kinetic energy formula, Radiant energy, Thermodynamic energy, Sound energy, Work-Energy theorem, Rotational kinetic energy.
Read More: Derivation of Equation of Motion in Physics
What is Kinetic Energy?
[Click Here for Sample Questions]
Kinetic energy is the measure of the work that an object does by virtue of its motion. The application of force needs work and once the work is done or complete, the energy in the object gets transferred to the object to move at a constant velocity.
- The same work is done when the body changes its current speed to a state of rest.
- The energy here is referred to as Kinetic energy.
- It depends on the speed and mass of an objection that is set in motion.
- Kinetic energy can also be defined as a property of a moving object or particle depending on its motion and the mass of the object.
- The motion can be a translation, vibration, or any combination of motions.
Kinetic energy
Read more:
| Physics related links: | ||
|---|---|---|
| Unit of Work | Radioactivity | Work Done |
| Types of springs | Work and Energy | Joule Thomson Effect |
Examples of Kinetic Energy
[Click Here for Sample Questions]
To better understand the concept of Kinetic energy let's consider the following examples seen in day-to-day life.
- The most common example of Kinetic energy is an airplane as it has huge Kinetic energy because of its faster velocity and huge mass.
- When a ball is thrown out, it will have a large amount of kinetic energy even though it is small and has less mass.
- A downhill skier coming down will have a large amount of Kinetic energy because of the high velocity and mass.
- When an asteroid falls on the earth, it raises a large amount of Kinetic energy.
- When comparing cars and trucks traveling on the road, a car has less kinetic energy as compared to a semi-truck because of the less mass of the car than a truck.
| Sample Questions: Ques. Is Kinetic Energy a scalar or a vector quantity? Ans. The velocity (v) is squared. As we know that the square of a vector quantity is a scalar. We also know that mass is a scalar quantity. Therefore, kinetic energy is a scalar quantity. |
The Formula for Kinetic Energy
[Click Here for Sample Questions]
The formula for kinetic energy for a body of mass m moving with velocity v is given by
| KE = 1/2mv2 |
Derivation of Kinetic Energy
Let a body move along a straight line with acceleration a, Starting from rest let it acquire velocity v after traveling distance s. Then, the equation of motion can be given by
v2 = u2 + 2as
Since the body is starting from rest, therefore u = 0
⇒ v2 = 2as ⇒ a = v2/2s
Force in the direction of displacement, F = ma
Substituting the value of a, we get
F = m(v2/2s)
Now, Work done, W = Fs cosθ = Fs cos0o = Fs
⇒ W = m(v2/2s) x s = 1/2 mv2
This work appears as Kinetic energy
⇒ K.E. = 1/2 mv2
Relation between Kinetic Energy and Linear Momentum
Let an object of mass m moving with velocity v, then its linear momentum is given by
p = mv ...(i)
And its kinetic energy is given by
K.E. = 1/2 mv2 ...(ii)
Multiplying and dividing equation (ii) by the mass of the body m, we get
K.E. = m2v2/2m
Using equation (i), we get
\(K.E.={p^2 \over 2m} \,\,or\,\,p=\sqrt {2m(K.E.)}\)
Rotational Kinetic Energy
The kinetic energy due to the rotation of an object is called rotational kinetic energy. It is directly proportional to the rotational moment of inertia and the square of the magnitude of the angular velocity.
The rotational kinetic energy of a rotating object is given by
\(K_r={1\over 2}I{\omega}^2\)
Where
- I = moment of inertia of the object
- ω = angular velocity
Work Energy Theorem
The work-energy theorem states that the work done by all forces on a particle is equal to the change in the particle’s kinetic energy.
According to the work-energy theorem
\(W_{total}=\Delta K.E.={1\over 2}mv_f^2-{1\over 2}mv_i^2\)
Where
- m = mass of the particle
- vi = initial velocity
- vf = final velocity
Units of Kinetic Energy
[Click Here for Sample Questions]
Taking the unit of mass as Kilogram (kg) and velocity as per meter per second. Therefore, the kinetic energy has a unit of kilograms per square second.
- Kinetic energy is measured in joules.
- The SI unit of Kinetic energy is Joules donated as J and the CGS unit of Kinetic energy is erg.
Kinetic energy Formula
Read More: Potential Energy Formula
Types of Kinetic Energy
[Click Here for Sample Questions]
The five types of kinetic energy are radiant, thermal, acoustic, electrical, and mechanical. Let's have a look at some kinetic energy examples and learn more about the different types of kinetic energy.
Radiant Energy
Radiant energy is a type of energy formed due to the motion due to any medium or space. Examples of radiant energy are-
- Rays (Gamma)
- Ultraviolet light.
Radiant energy
Thermodynamic Energy
Thermal energy is known as heat energy and is created when atoms collide. This type of energy is formed due to the faster movements of atoms as they collide. Some examples of thermal energy are:
- Natural hot springs
- The swimming pool is heated
Thermodynamic Energy (Natural Spring)
Sound Energy
When an object vibrates, sound energy is produced. This type of energy is formed due to objects' vibration. For example- In a vacuum, sound energy travels through the medium but, there are no particles to act as a medium
Electrical Energy
Electrical energy is provided by free electrons, both positive and negative in charge. For example-
- Batteries that are being used
- Lightning
Electrical Energy
Mechanical Energy (Energy Produced by Machines)
Mechanical energy is a formed sum of potential and kinetic energy. Mechanical energy cannot be created or destroyed but can be converted from one form to another. For example-
- A satellite orbiting around the earth
- A moving vehicle
Mechanical Energy( Energy Produced by Machines)
Also Check Out:
| Important Topics Related to Motion in Physics | ||
|---|---|---|
| Distance and Displacement | Motion in a Straight Line | Uniform Circular Motion |
| Type of Motion Measurement | Laws of Motion MCQs | Wave Motion |
What is Potential Energy?
[Click Here for Sample Questions]
Potential energy is the form of energy by which the energy of an object or particle is stored due to some position and in contrast to some other position at rest is known as potential energy. Potential energy is measured in joules and measured based on the distance, height, or mass of the object.
Examples of Potential Energy
To better comprehend the topic of potential energy let's consider some examples given below.
- At the cliff edge, the rocket is there, and when the rocks fall the potential energy gets transferred to kinetic energy.
- In nature, when their branches fall on the ground, it means that they have potential energy.
- Food that everyone takes provides us with energy due to potential energy.
- Crane when swigs gain potential energy.
Difference Between Kinetic Energy and Potential Energy
The difference between Kinetic energy and Potential energy is as follows:
| Kinetic Energy | Potential Energy |
|---|---|
| The Energy possessed by a body due to its motion is called Kinetic energy. | The Energy possessed by a body due to its change in position or shape is called potential energy. |
| The kinetic energy of an object is relative to other moving or stationary objects in the environment. | The potential energy of an object is not relative to the environment. |
| It can be transferred from one object to another object during a collision. | It cannot be transferred from one object to another object. |
| Kinetic energy is given by, K.E. = 1/2 mv2 | Potential energy is given by, P.E. = mgh |
Read More: Derivation of Equation of Motion in Physics
Previous Years’ Questions
- Calculate the reading of the spring balance when a mass of 5kg is suspended on an inclined plane. [BITSAT 2006]
- Calculate the impulse experienced by the body which hits a rigid wall. [BITSAT 2018]
- What is the apparent weight of the man moving up the elevator? [DUET 2003]
- What is the work done by the inextensible spring? [BITSAT 2013]
- How much time would the man take to move up the elevator? [NEET 2006]
- What is the minimum stopping distance of the automobile? [KEAM 2003]
- Identify the correct scenario for three objects thrown in the air. [JKCET 2007]
- An example of an inertial frame observer is? [JKCET 2009]
- Calculate the time needed by the body to cover 1/4th of the distance from a state of rest. [JIPMER 1999]
- What is the change in the magnetic field of a charged particle which enters a uniform magnetic field? [JKCET 2006]
Things To Remember
- The energy that an item or particle obtains as a result of its movement is known as kinetic energy. An item accelerates and creates energy when a net force is applied to it.
- Moving things or particles have this energy as a quality. Furthermore, not only does motion affect this energy, but so does mass.
- The kinetic energy of an object is related to its velocity squared. This means that doubling the object's velocity quadruples its kinetic energy.
- K.E. must be either zero or positive at all times.
- The scalar quantity of kinetic energy is measured in Joules.
Sample Questions
Ques. A bicycle has a mass of 10 kilograms and travels at a constant speed of 10 km/h. Find out how much kinetic energy this bicycle has. (3 marks)
Ans. "m'" is the mass, while "v" is the velocity. m = 10 kg and v = 10 km/h are also used. Now it's time to use the kinetic energy equation:
Ek=½ mv2
Ek = ½ (10 kg) (10km/h)
Ek = 50 Joules
As a result, the kinetic energy is 50 Joules in this situation.
Ques. Assume a 2kg ball moves at a speed of 10m/s. Find out how much kinetic energy it has. (3 marks)
Ans. Given: m = 2 kg; v = 10 m/s;
The KE is produced by,
K.E=½ mv2
=K.E.=½ (2)(10)2
K.E.= 100 joules
Ques: What is the velocity of 100g having a kinetic energy of 20 Joules? (2 marks)
Ans. 100gm=0.1kg
KE=(1/2)x mv2
20=(1/2)x0.1x v2
20x2=0.1x v2
400= v2
v=20m/s
Ques. When you run faster, what happens to your kinetic energy? (2 marks)
Ans. The kinetic energy of an object appears to rise with the square of its speed. An automobile traveling at 40 mph has four times the kinetic energy of one traveling at 20 mph, while a car traveling at 60 mph has nine times the kinetic energy of one traveling at 20 mph. As a result, even a little increase in speed can result in large kinetic energy.
Ques. What is the best way to store kinetic energy? (2 marks)
Ans. Potential energy is a term used to describe the amount of energy Kinetic energy is a type of energy that can be stored. Potential energy is turned back into kinetic energy when we drop the object from the shelf or release the spring. In a collision, kinetic energy can be transferred from one body to another, which can be elastic or inelastic.
Ques. Is kinetic energy responsible for motion? To have kinetic energy, what must an object be doing? (2 marks)
Ans. Kinetic energy is a type of energy that an item or particle possesses as a result of its motion. Kinetic energy is a property of a moving object or particle defined by both its mass and its velocity.
Kinetic energy is the energy that a thing has when it is moving. When something has kinetic energy, it is moving. Potential Energy is defined as The energy held in an object as a result of its position is known as potential energy.
Ques. Is the energy in batteries potential or kinetic? (2 marks)
Ans. Is the energy in a battery kinetic or potential? Batteries store energy in the bonds of molecules contained within the battery acid at their core, making them a type of chemical energy. The keyword here is "stored," which indicates that batteries are classified as a sort of potential energy, which is how all chemical energy is classified.
Ques. What are the effects of mass and speed on kinetic energy? (2 marks)
Ans. Two variables influence the amount of translational kinetic energy (from now on, the word kinetic energy will refer to translational kinetic energy) that an item has: the object's mass (m) and its speed (s) (v)... The kinetic energy is determined by the square of the speed.
Ques. A boy is transporting a cupboard of mass 6kg with a kinetic energy of 40 Joules. Find the velocity at which the boy is running. (2 marks)
Ans: Mass, m = 6 Kg
Kinetic energy K.E = 60 J
The man is running with a velocity of 3.65m/s
Ques: A truck is traveling at a velocity of 10m/s and has a mass of 250 kg. What would be its kinetic energy? (2 marks)
Ans. Mass of the truck- 250 kg
Velocity donated by V - 10m/s
Kinetic energy K.E- =12500 kgm2s2
Also Check:
Comments