What is Kinetic Energy?
Kinetic energy is defined as the energy that is produced by an object due to its motion. When an object is set to acceleration, there is a definite need to apply certain forces. The application of force needs work, and after the work is done, the energy gets transferred to the object making it move at a constant velocity.
Here, the energy transferred is referred to as kinetic energy and depends on the speed and mass of the object being set in motion.
Fun Facts: As we move ahead on this page, you will understand how energy in an object changes from one form to another. For instance, take a flying squirrel that has collided with a chipmunk in its rest state. After the collision, there will be a flow of kinetic energy resulting in the squirrel to transform its energy into some other forms. It will come to rest and then the kinetic energy will be zero.
How Can We Calculate Kinetic Energy?
In order to find out the kinetic energy, there needs to be some reasoning platform. Some of the findings are required, like the work done (W), by force (F). So, for instance, consider a box of mass m that is being pushed to a distance d because of the application of a force parallel to the surface.
Looking at the definition of work done, it is the product of force and distance.
W=F⋅d
=m⋅a⋅d
From the kinematic equations of motion, it is stated that we could substitute the acceleration a if the initial and final velocity v and v0 and the distance d. Is given:
So, from that, we derive:
\[ v^{2} = v_{0}^{2} + 2ad \]
gives us, \[a = \frac{v^{2} + v_{0}^{2}}{2d}\]
When a net amount of work is done, the kinetic energy K does change.
Kinetic Energy: \[ K = \frac{1}{2} m v^{2}\]
In other words, the change in kinetic energy is equal to the net work done on a system or an object.
\[ W _{net} = \triangle K \]
The above-mentioned formula is said to be the work-energy theorem and applies in a general sense. When forces act in different magnitudes and directions, it is imperative to know the conservative forces and conservation of energy. Here, the conservative force is a force where the total work done in any moving object between two definite points is independent of the path taken. Whereas, the conservation of energy states that the sum total energy of any isolated system doesn’t change over the time.
Examples of Kinetic Energy and Potential Energy
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Kinetic Energy Examples
Bearing in mind the above formula for kinetic energy, look at a few of the examples seen in everyday life situations.
An aeroplane has huge kinetic energy in flight because of its faster velocity and huge mass.
A baseball after it is thrown, it will have a large amount of kinetic energy because of its high velocity, and despite its smaller size and mass.
A downhill skier coming down from above will show immense kinetic energy because of its high velocity and mass.
Before a golf ball has been struck shows zero kinetic energy as its velocity is zero.
When an asteroid falls at an incredible speed, it has a huge amount of kinetic energy.
A car travelling down the road has less kinetic energy as compared to that of a semi-truck because of the less mass of the car than the truck.
What is Potential Energy?
The form of energy by virtue of which energy is stored in an object due to some position and relative to some other position at rest is known as potential energy. Three types of energy effects are shown here viz: nuclear energy, chemical, and potential electrical. This can be measured based on the distance, height, or mass of the object. It is measured in Joules.
Examples of Potential Energy:
A rocket sitting at the cliff's edge. When the rock falls, the potential energy gets converted to kinetic energy.
Tree branches up high can fall into the ground, so they have potential energy.
A dynamite stick has chemical potential energy. After the release, it will get fused to contact with the chemical; it will be activated.
Foods that we intake provide us with energy due to the chemical potential energy. It helps with basic metabolic activities inside us.
A spring stretched in a pinball machine can move the call after it is released. This produces elastic potential energy.
Crane, when swings in a wrecking ball gain much energy even to crash the buildings
Kinetic Energy Units
When we take the unit of mass as kilogram and velocity as a metre per sec, the kinetic energy has the unit of kilograms metre square per Second Square. It is usually measured in Joules. So, the SI unit of kinetic energy is Joule (J), which is precisely 1kg.m2.
Conclusion
Kinetic energy is the energy generated by an object as a result of its motion. There is a clear necessity to apply forces when an item is set to accelerate. Work is required for the application of force, and after the work is completed, the energy is delivered to the object.
FAQs on Kinetic Energy
1. What is the definition of kinetic energy?
Kinetic energy is the energy an object possesses due to its motion. When an external force does work on an object, that object gains energy and moves. This energy of motion is called kinetic energy. It depends directly on two factors: the object's mass and its velocity. The faster an object moves or the more massive it is, the greater its kinetic energy will be.
2. What is the formula for calculating kinetic energy?
The formula to calculate kinetic energy (KE) is: KE = ½ mv². In this equation, 'm' represents the mass of the object in kilograms (kg), and 'v' represents the velocity of the object in meters per second (m/s). This formula shows that kinetic energy increases with the square of the velocity.
3. What is the SI unit of kinetic energy?
The SI unit of kinetic energy is the Joule (J). This is the same unit used for all forms of energy and work. One Joule is equivalent to the work done when a force of one Newton is applied over a distance of one meter. In terms of base SI units, one Joule is equal to one kilogram meter squared per second squared (kg·m²/s²).
4. What are some common examples of kinetic energy in daily life?
Kinetic energy is present in any moving object. Some common examples include:
- A moving car travelling on a road.
- A bowling ball rolling down the lane towards the pins.
- A planet, like Earth, orbiting the Sun.
- A person running or walking.
- The wind, which is the movement of air molecules.
- An aeroplane flying through the sky.
5. How is kinetic energy different from potential energy?
The primary difference between kinetic and potential energy lies in their source. Kinetic energy is the energy of motion, possessed by an object that is actively moving. In contrast, potential energy is stored energy an object has due to its position, state, or configuration. For example, a rolling ball has kinetic energy, while a ball held at a height has gravitational potential energy which converts to kinetic energy once it's dropped.
6. How is the formula for kinetic energy, KE = ½ mv², derived?
The formula for kinetic energy is derived from the definition of work. According to the Work-Energy Theorem, the work done (W) on an object by a net force equals the change in its kinetic energy. Consider an object of mass 'm' starting from rest (initial velocity u=0) and accelerating to a final velocity 'v' over a distance 'd'.
- Work done is force times distance: W = F × d.
- From Newton's second law, Force is mass times acceleration: F = m × a. So, W = (m × a) × d.
- Using the third equation of motion, v² = u² + 2ad. Since u=0, we get v² = 2ad, which means ad = v²/2.
- Substituting 'ad' back into the work equation gives: W = m × (v²/2).
- Since the work done is equal to the kinetic energy gained, we get KE = ½ mv².
7. Can the kinetic energy of an object ever be negative?
No, the kinetic energy of an object can never be negative. The reason lies in its formula, KE = ½ mv². In this formula, the mass (m) of an object is always a positive scalar quantity. The velocity (v) can be positive or negative depending on the direction of motion, but it is squared in the formula. The square of any real number (positive or negative) is always non-negative (zero or positive). Therefore, since both mass and velocity squared are non-negative, their product, the kinetic energy, can only be positive or zero (if the object is at rest).
8. How does doubling the velocity of an object affect its kinetic energy?
Doubling the velocity of an object makes its kinetic energy four times greater. This is because kinetic energy is directly proportional to the square of the velocity (KE ∝ v²). If the initial velocity is 'v', the kinetic energy is KE₁ = ½ mv². If the velocity is doubled to '2v', the new kinetic energy will be KE₂ = ½ m(2v)² = ½ m(4v²) = 4 × (½ mv²). Thus, KE₂ = 4 × KE₁. This relationship explains why high-speed collisions are significantly more destructive.
9. What is the relationship between work done on an object and its kinetic energy?
The relationship between work and kinetic energy is described by the Work-Energy Theorem. This fundamental principle states that the net work done on an object by all forces is equal to the change in its kinetic energy (ΔKE).
- If positive net work is done on an object, its speed and kinetic energy increase.
- If negative net work is done on an object (e.g., by friction), its speed and kinetic energy decrease.
- If the net work done is zero, the object's kinetic energy remains constant.
