Kinetic Energy: Definition, Formula, Examples, Questions, Equation

Q: What is the kinetic energy of an object?

The kinetic energy of an object is written by K.E=1/2 mv 2

Kinetic Energy - Definition, Examples, Formula, FAQs

Edited By Vishal kumar | Updated on Jul 02, 2025 04:30 PM IST

Kinetic energy is the energy of motion, and it's a fundamental force that shapes our world. Whether it's a car speeding down the highway, a soccer ball flying through the air, or even the simple act of walking, kinetic energy is at play. It moves objects, tells us about their speed, and helps us understand the concept of momentum. By exploring kinetic energy, we can appreciate the beauty and simplicity of this powerful force and see how it influences our everyday lives

This Story also Contains

Definition of Kinetic Energy
Kinetic Energy Examples
Formula of Kinetic Energy
Unit of Kinetic Energy
Types of kinetic energy
Difference between Kinetic Energy and Potential Energy
Solved Example Based On Kinetic Energy

Kinetic Energy - Definition, Examples, Formula, FAQs

In this article, we are going to study kinetic energy, how it depends on the frame of reference, the work-energy theorem, and its relationship with linear momentum. This topic falls under the broader category of work, energy, and power, which is a crucial chapter in Class 11 physics. It is not only essential for board exams but also for competitive exams like the Joint Entrance Examination (JEE Main), National Eligibility Entrance Test (NEET), and other entrance exams such as SRMJEE, BITSAT, WBJEE, BCECE and more. Over the last ten years of the JEE Main exam (from 2013 to 2023), more than ten questions have been asked on this concept. And for NEET four questions were asked from this concept.

Let's read this entire article to gain an in-depth understanding of Kinetic energy.

Definition of Kinetic Energy

Kinetic energy meaning: it is the energy created by an object as a result of its motion. When an object is set to accelerate, it is imperative that specific forces be applied. Work is required to apply force, and once the work is completed, the energy is transmitted to the object, causing it to move at a constant velocity. The word kinetic meaning is something related to or resulting from motion. The energy transferred is referred to as kinetic energy in this case, and it is dependent on the speed and mass of the object.

Kinetic Energy definition

“The kinetic energy of an object is known as the energy obtained by the object because of its motion.”

Also read -

NEET Highest Scoring Chapters & Topics

This ebook serves as a valuable study guide for NEET exams, specifically designed to assist students in light of recent changes and the removal of certain topics from the NEET exam.

Download E-book

How does Kinetic Energy get transferred?

Kinetic energy is a type of energy that may be exchanged between objects and turned into other forms of energy. The yo-yo is an excellent illustration of kinetic energy transformation. When you first start playing with it, you should let it rest in your hand; at this time, all of the energy is stored in the ball as potential energy. When a person drops the yo-yo, the stored energy is converted into kinetic energy or movement energy. All of the energy in the ball is transformed into kinetic energy once it reaches the bottom of the yo-yo. As it returns to the hand, all of the energy is transformed back to potential energy.

Kinetic energy transform

There is a ball (Image-1) that has potential energy, when we dropped the ball (Image-2) the ball started falling and now it has Kinetic Energy.

Learn kinetic Energy Better from the Given Video Below

Kinetic Energy Examples

Here are some daily-life examples of kinetic energy…

Moving car
Bullet from gun
Throw of a ball
Windmills
Running

Formula of Kinetic Energy

The kinetic energy is given by the following formula

$\mathrm{K.E}=1 / 2 \mathrm{MV}^2$

Where M is the mass of the object, V is the velocity of the object and KE is kinetic energy.

Related Topics,

Unit of Kinetic Energy

The SI unit of kinetic energy is the joule.

1 joule $=\mathrm{Kg} \cdot \mathrm{m}^2 \cdot \mathrm{~s}^{-2}$

The CGS unit of kinetic energy is erg.

How can we calculate Kinetic Energy?

We know that work done is written as …

W= f.d = m.a.d ……….(1)

We know that $v_f^2-v_i^2=2 a d, d=\left(v_f^2-v_i^2\right) / 2 a$
placing the value of ' d' in equation(1)

$$
\begin{aligned}
& \text { Then.. } W=m \cdot a \cdot\left(v_f^2-v_i^2\right) / 2 a \\
& =1 / 2 m\left(v_f^2-v_i^2\right) \\
& =1 / 2 m v_f^2-1 / 2 m v_i^2
\end{aligned}
$$

Types of kinetic energy

Kinetic energy has five types

types of kinetic energy

Radiant energy

It is a type of kinetic energy that is always in motion. Examples of radiant energy…

Ultraviolet light
Gamma rays
Beta ray

Thermal energy

Thermal energy, often known as heat energy, is produced when atoms clash with each other. The following are some examples of thermal energy:

The warmth of the sun
A cup of hot milk
Explosion of firecrackers

Sound energy

It is produced by vibrating an object, it always travels in the medium. It can’t travel by vacuum. Examples of sound energy are:

Tuning fork
Beat of drum
Sound of hor

Electrical energy

The free electrons, both positive and negative in charge, provide electrical energy. The following are some examples of electrical energy:

Battery
Lightning

Mechanical energy

The sum of kinetic energy and potential energy is known as mechanical energy.

Examples:

A moving truck
A rocket in orbit

Difference between Kinetic Energy and Potential Energy

Kinetic energy	Potential energy
The energy created by an object as a result of its motion is known as kinetic energy.	The energy created by an object due to its position or state.
The formula of kinetic energy is K.E=1/2 mv²	The formula of potential energy is mgh
Vibrational energy is an example of kinetic energy.	Gravitational potential energy is an example of potential energy.

Solved Example Based On Kinetic Energy

Example 1: An athlete of mass 50kg in the Olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range

1) 2,000 J−5,000 J
2) 200 J−500 J
3) 2×105 J−3×105 J
4) 20000 J−50000 J

Solution:

Kinetic energy

k=12mv2
wherein
m→ mass
v→ velocity

Kinetic energy is never negative

Kinetic energy

Initial velocity = 0

Final velocity $=v_f$
$S=u t+12 \mathrm{at} 2 \Rightarrow 100=0+12 \times \mathrm{a} \times 100 \mathrm{a}=2 \mathrm{~m} / \mathrm{s} 2$
Maximum speed $(a)=20 \mathrm{~m} / \mathrm{s} 2$
Maximum K.E. $=12 \mathrm{mv} 2=12 \times 50 \times 400=10,000 \mathrm{~J}$
Maximum speed (a) $=20 \mathrm{~m} / \mathrm{s} 2$
Maximum K.E. $=12 \mathrm{mv} 2$

If it runs with constant velocity $\mathrm{v}=10 \mathrm{~m} / \mathrm{s}$
Then K.E. $=12 \times 50 \times 100=2500$
So it lies between 2500 to $10,000 \mathrm{~J}$.

Example 2: The average mass of raindrops is $3.0 \times 10-5 \mathrm{~kg}$ and their average terminal velocity is $9 \mathrm{~m} / \mathrm{s}$. Calculate the energy transferred by rain to each square meter of the surface at a place that receives 100 cm of rain in a year.
3. 5×105 J
2) 4.05×104 J
3) 3.0×105 J
4) 9.0×104 J

Solution:

Total volume of water in 1 m 2 area

$$
=1 \mathrm{~m} 2 \times 100 \mathrm{~cm}=1 \mathrm{~m} 3
$$

Total mass in 1 m 2 area $=\rho \vee=103 \times 1 \mathrm{Kg}=103 \mathrm{Kg}$

Kinetic energy $=1 / 2 \times 103 \times 92=4.05 \times 104 \mathrm{~J}$
Hence, the answer is option (2).

Frequently Asked Questions (FAQs)

1. What is the kinetic energy of an object?

The kinetic energy of an object is written by K.E=1/2 mv²

2. What is the SI unit of kinetic energy?

The SI unit of kinetic energy is the joule.

3. Can kinetic energy be negative?

NO, kinetic energy cant be negative because of the square of velocity gives positive and mass

Never be negative.

4. Can kinetic energy be negative?

No, kinetic energy cannot be negative. Since it's calculated using the square of velocity (v²) and mass is always positive, the result is always positive or zero (when the object is at rest).

5. Which condition is required for maximum kinetic energy?

Kinetic energy is maximum when velocity is maximum and mass is in equilibrium, position

6. What is kinetic energy?

Kinetic energy is the energy possessed by an object due to its motion. It is the energy of movement and depends on both the mass of the object and its velocity. The faster an object moves or the more massive it is, the more kinetic energy it has.

7. What is the kinetic energy of an object at rest?

An object at rest has zero kinetic energy. Kinetic energy is only associated with motion, so when velocity is zero, kinetic energy is also zero, regardless of the object's mass.

8. Why does a moving car still have kinetic energy even when the engine is turned off?

A moving car has kinetic energy due to its motion, regardless of whether the engine is running. The car gained this energy from the work done by the engine earlier. It will continue moving (and have kinetic energy) until friction brings it to a stop.

9. Why do asteroids pose a threat to Earth despite their relatively small size?

Asteroids pose a threat due to their extremely high kinetic energy. Even though they may be small, their enormous velocities result in massive kinetic energies that would be released upon impact with Earth.

10. How does kinetic energy affect the pressure of a gas?

The pressure of a gas is caused by the collisions of gas molecules with the container walls. Higher kinetic energy of the molecules (due to higher temperature) results in more forceful collisions and thus higher pressure.

11. How is kinetic energy different from potential energy?

Kinetic energy is associated with motion, while potential energy is associated with position or configuration. Kinetic energy is the energy an object has because it's moving, whereas potential energy is stored energy that can be converted to kinetic energy.

12. How does air resistance affect the kinetic energy of a falling object?

Air resistance opposes the motion of a falling object, causing it to lose kinetic energy. Some of the object's gravitational potential energy is converted to heat energy due to air friction instead of being fully converted to kinetic energy.

13. How does kinetic energy relate to work?

The work-energy theorem states that the net work done on an object equals its change in kinetic energy. When positive work is done on an object, its kinetic energy increases, and when negative work is done, its kinetic energy decreases.

14. What's the relationship between kinetic energy and momentum?

While both kinetic energy and momentum depend on mass and velocity, they are different quantities. Momentum is mass times velocity (p = mv), while kinetic energy is half mass times velocity squared (KE = 1/2mv²). Kinetic energy is a scalar quantity, while momentum is a vector.

15. What happens to kinetic energy when an object stops moving?

When an object stops moving, its kinetic energy becomes zero. The energy is typically converted into other forms, such as heat due to friction, sound energy, or potential energy if the object's position changes.

16. What is the formula for kinetic energy?

The formula for kinetic energy is KE = 1/2 × m × v², where KE is kinetic energy, m is the mass of the object, and v is its velocity. This equation shows that kinetic energy increases linearly with mass but quadratically with velocity.

17. Why does the kinetic energy formula have a "1/2" in it?

The "1/2" in the kinetic energy formula comes from the mathematical derivation of the equation. It arises from integrating the force with respect to distance when calculating the work done to accelerate an object from rest to a given velocity.

18. Does kinetic energy depend more on mass or velocity?

Kinetic energy depends more on velocity than mass. While it increases linearly with mass (doubling mass doubles kinetic energy), it increases quadratically with velocity (doubling velocity quadruples kinetic energy). This is why small, fast-moving objects can have high kinetic energy.

19. Why do cars with the same mass but different speeds have different stopping distances?

Cars with higher speeds have more kinetic energy. Since the work required to stop a car (by friction) is equal to its initial kinetic energy, cars with higher speeds require more work to stop, resulting in longer stopping distances.

20. Why do moving charges have kinetic energy?

Moving charges, like electrons in an electric current, have kinetic energy because they have mass and velocity. This kinetic energy of charges is the basis for electrical energy and can be converted to other forms, such as heat in resistors or light in LEDs.

21. How is kinetic energy involved in hydroelectric power generation?

In hydroelectric power, the gravitational potential energy of water at height is converted to kinetic energy as it falls. This kinetic energy is then used to turn turbines, which convert it into electrical energy through generators.

22. Why does a satellite in orbit have kinetic energy even though it appears to be "floating" in space?

A satellite in orbit is actually in constant free fall around the Earth. It has a large horizontal velocity that gives it kinetic energy. This kinetic energy balances the gravitational potential energy, allowing the satellite to maintain its orbit.

23. How does kinetic energy change during free fall?

During free fall (ignoring air resistance), an object's kinetic energy increases as it falls. Gravitational potential energy is continuously converted to kinetic energy, causing the object to accelerate and gain speed.

24. How does the kinetic energy of an object change as it moves in a circular path at constant speed?

The magnitude of the kinetic energy remains constant for an object moving in a circular path at constant speed. However, the velocity vector (direction) is continuously changing, resulting in centripetal acceleration.

25. What's the difference between translational, rotational, and vibrational kinetic energy?

Translational kinetic energy is associated with linear motion of an object's center of mass. Rotational kinetic energy is due to an object's rotation around an axis. Vibrational kinetic energy is associated with the back-and-forth motion of atoms within molecules or solids.

26. How is kinetic energy related to temperature in gases?

In gases, temperature is a measure of the average kinetic energy of the molecules. Higher temperatures correspond to greater average kinetic energies of the gas molecules.

27. What happens to kinetic energy in an elastic collision?

In a perfectly elastic collision, the total kinetic energy of the system is conserved. The kinetic energy may be redistributed between the colliding objects, but the sum of their kinetic energies before and after the collision remains the same.

28. How does kinetic energy change in an inelastic collision?

In an inelastic collision, some kinetic energy is converted to other forms of energy, such as heat or sound. The total kinetic energy of the system after the collision is less than before the collision.

29. Why do spacecraft need to shed kinetic energy when landing on a planet?

Spacecraft need to reduce their kinetic energy when landing to avoid crashing. This is typically done through atmospheric drag, parachutes, or retro-rockets, which convert the craft's kinetic energy into heat or work against gravity.

30. How does kinetic energy relate to the concept of power?

Power is the rate at which work is done or energy is transferred. In the context of kinetic energy, power can be thought of as how quickly kinetic energy is changing. For example, a more powerful engine can increase a car's kinetic energy more rapidly.

31. How does kinetic energy affect the damage caused by bullets?

The damage caused by bullets is largely due to their kinetic energy. Despite their small mass, bullets have very high velocities, giving them substantial kinetic energy. This energy is transferred to the target upon impact, causing damage.

32. How does kinetic energy relate to the concept of escape velocity?

Escape velocity is the minimum velocity an object needs to escape a planet's gravitational field. It's determined by equating the object's kinetic energy to the gravitational potential energy needed to move infinitely far from the planet.

33. Can two objects with different masses have the same kinetic energy?

Yes, two objects with different masses can have the same kinetic energy. A less massive object moving at a higher velocity can have the same kinetic energy as a more massive object moving at a lower velocity.

34. What role does kinetic energy play in nuclear fission reactions?

In nuclear fission, the kinetic energy of the resulting fragments is a significant portion of the energy released. These high-speed fragments collide with other atoms, transferring their kinetic energy and heating the surrounding material.

35. How does kinetic energy affect car safety design?

Car safety features are designed to increase the time over which kinetic energy is dissipated during a collision. Crumple zones, airbags, and seat belts all work to extend the time of impact, reducing the force experienced by occupants.

36. What happens to the kinetic energy of water molecules when they evaporate?

When water molecules evaporate, they gain kinetic energy. This additional energy allows them to overcome the attractive forces between molecules in the liquid state and escape into the gas phase.

37. Why do heavier objects require more work to lift, but not necessarily more work to move horizontally?

Lifting an object increases its gravitational potential energy, which depends on mass. However, moving an object horizontally only requires overcoming friction, which doesn't necessarily increase with mass. The kinetic energy needed for horizontal motion depends on the desired velocity, not the mass.

38. How does kinetic energy relate to the concept of terminal velocity?

Terminal velocity is reached when the upward drag force equals the downward gravitational force on a falling object. At this point, the object's kinetic energy remains constant because it's no longer accelerating, despite continuing to fall.

39. What happens to kinetic energy in a system where friction is present?

In a system with friction, kinetic energy is gradually converted into thermal energy (heat). This is why moving objects eventually come to a stop unless a force is continuously applied to maintain their motion.

40. How is kinetic energy related to the damage caused by hurricanes and tornadoes?

The destructive power of hurricanes and tornadoes comes from the kinetic energy of their high-speed winds. This energy can be transferred to objects, causing them to move and collide with other objects, resulting in widespread damage.

41. What role does kinetic energy play in the function of a pendulum?

In a pendulum, there's a continuous exchange between kinetic and potential energy. At the highest points, the pendulum has maximum gravitational potential energy and minimum kinetic energy. At the lowest point, it has maximum kinetic energy and minimum potential energy.

42. How does kinetic energy affect the design of roller coasters?

Roller coaster design relies heavily on the conversion between potential and kinetic energy. The initial climb converts chemical energy (from the lift motor) to gravitational potential energy, which is then converted to kinetic energy during the descent. The track layout is designed to manage this energy conversion while providing thrills and ensuring safety.

43. Why does a gun recoil when fired?

Gun recoil is a consequence of conservation of momentum and energy. When a bullet is fired, it gains kinetic energy and momentum. To conserve momentum, the gun must move in the opposite direction. This backward motion of the gun represents its recoil kinetic energy.

44. How does kinetic energy relate to the concept of braking distance in vehicles?

Braking distance is directly related to a vehicle's kinetic energy. The work done by the brakes must equal the initial kinetic energy of the vehicle to bring it to a stop. Higher speeds result in much greater kinetic energies, requiring significantly longer braking distances.

45. What happens to the kinetic energy of air molecules in a bicycle pump as the piston is pushed in?

As the piston is pushed in, the air molecules are compressed into a smaller volume. This increases their kinetic energy, which is observed as an increase in temperature of the air inside the pump.

46. How does kinetic energy affect the impact force in sports like boxing or football?

The impact force in contact sports is related to the change in kinetic energy over time. A punch or tackle transfers the kinetic energy of the moving athlete or body part to the opponent. The larger the kinetic energy and the shorter the impact time, the greater the force experienced.

47. How does kinetic energy relate to the concept of horsepower in engines?

Horsepower is a measure of power, which is the rate of energy transfer. In the context of engines, it represents how quickly the engine can increase the kinetic energy of a vehicle. More horsepower means the engine can accelerate the vehicle more rapidly, increasing its kinetic energy faster.

48. What role does kinetic energy play in the function of a hydraulic press?

In a hydraulic press, the kinetic energy of the fluid (usually oil) is converted into potential energy in the form of pressure. This pressure is then used to exert large forces. The work done by the press is ultimately derived from the kinetic energy input to the system.

49. How does kinetic energy affect the design and function of shock absorbers in vehicles?

Shock absorbers are designed to dissipate the kinetic energy of the vehicle's up-and-down motion. They convert this kinetic energy into heat through fluid friction, improving ride comfort and maintaining better contact between the tires and the road.

50. Why does a trampoline "store" energy when you land on it?

When you land on a trampoline, your kinetic energy is temporarily converted into elastic potential energy as the trampoline's surface stretches. This elastic potential energy is then converted back into kinetic energy as the trampoline springs back, propelling you upward.

51. How does kinetic energy relate to the concept of momentum in collisions?

While momentum is conserved in all collisions, kinetic energy is only conserved in elastic collisions. In inelastic collisions, some kinetic energy is converted to other forms. The relationship between kinetic energy and momentum is key to understanding and analyzing collision physics.

52. What role does kinetic energy play in the process of nuclear fusion in stars?

In stars, extremely high temperatures provide hydrogen nuclei with enough kinetic energy to overcome their electrostatic repulsion and get close enough for the strong nuclear force to take effect, enabling fusion. This process releases energy and is the source of a star's power.

53. How does kinetic energy affect the flight of a boomerang?

The flight of a boomerang involves complex interactions of kinetic energy. The initial kinetic energy from the throw, combined with the rotational kinetic energy and the aerodynamic forces created by its shape, result in its characteristic curved flight path and return to the thrower.

54. Why does a spinning ice skater speed up when they pull in their arms?

This is due to the conservation of angular momentum. As the skater pulls in their arms, their moment of inertia decreases. To conserve angular momentum, their angular velocity must increase. This results in an increase in rotational kinetic energy, which comes from the work done by the skater's muscles in pulling in their arms.