What is kinetic energy?
Kinetic energy is the energy of movement. You see it when things move, like a walking person or a falling crumb. Anything that moves has kinetic energy. Something has no kinetic energy if it is not in motion.
Objects that don’t move have potential energy. This energy can turn into kinetic energy when something makes the object move, like gravity. A stretched rubber band, for instance, possesses potential energy. Release it, and it becomes kinetic energy.
Energy cannot be created or destroyed, under the rule of conservation of energy. It is solely capable of changing forms. For example, a swinging pendulum goes back and forth between kinetic and potential energy. At the highest point, it has the most potential energy and no kinetic energy. At the lowest point, it has the most kinetic energy and no potential energy. The total amount of energy stays the same, always changing between kinetic and potential energy.
Types of Kinetic Energy
A pendulum’s total energy is called mechanical energy, which includes both potential and kinetic energy. Many everyday objects have mechanical energy. This includes a person running, a spinning windmill, a flowing river, a satellite orbiting the earth, and an apple falling from a tree. Potential energy can be elastic, chemical, gravitational, or another type.
Besides mechanical energy, there are other common types of energy:
- Electrical Energy: The energy of electrons in motion, known as electrical energy, belongs to a certain type of motion. This phenomenon can be perceived in various forms, such as lightning, electric eels, brain waves, flashlights, lamps, and railroad signals.
- Radiant Energy: Radiant energy is the type that transmits through EM waves, e.g. microwaves, UV light, gamma rays, and visible light. Examples include sunlight, radio waves, light bulbs, X-ray machines, and the heating elements of toasters.
- Thermal Energy: The motion and collision of atoms and molecules emitting this energy called heat energy are thermal energy. Examples of this are boiling water, baking bread, geothermal hot springs, and the sun warming the earth’s atmosphere.
- Sound Energy: This energy moves in waves through materials like air or water. Sound cannot travel through a vacuum. Examples include someone singing, hands clapping, a drum beating, a buzzing insect, and an exploding firecracker. Not all sound is audible to humans, like ultrasound used in medical devices or sounds only certain animals can hear.
Examples of kinetic energy
- An asteroid falling to Earth has a lot of kinetic energy because it is big and moves fast.
- Given its size and speed, an airplane possesses a high kinetic energy when in flight.
- Walking gives you kinetic energy because you are moving your legs and body.
- When you throw a ball, it gets kinetic energy as it moves through the air. The faster you throw it, the more kinetic energy it has.
- Objects falling to the ground gain kinetic energy because of gravity. The impact’s kinetic energy depends on the object’s mass and speed.
- A truck on the road has more kinetic energy than a car at the same speed because the truck is much heavier.
Measuring Kinetic Energy
Kinetic energy is usually measured in Joules (J) and depends on an object’s mass (m) and velocity (v). The formula is:
KE=12mv2\text{KE} = \frac{1}{2} mv^2KE=21mv2
KE stands for kinetic energy. In the formula, velocity is squared, and mass is halved. This means kinetic energy is half the object’s mass times the velocity squared. More mass and higher velocity mean more kinetic energy.
For example, if an item has a mass of 10 kilograms (kg) and a pace of 15 meters in step with 2d (m/s), its kinetic electricity is 1125 J.The kinetic energy rises to 4500 J if the rate is doubled to 30 m/s. This explains why a vehicle hitting a barrier at 20 mph causes extra harm than one hitting at 10 mph.
This formula is for translational movement, where an object moves from one place to another. There are other types of kinetic movement:
- Translational: The object moves in a straight line, like a train traveling between stations.
- Rotational: The object spins around an axis, like the Earth rotating.
- Vibrational: The object vibrates, like a vibrating phone or an atom in a solid.
Some sources only mention translational and rotational movement, while others recognize more types but agree these are the main ones. An object can also have multiple types of movement, like a molecule that both rotates and vibrates.
Kinetic energy is calculated differently for non-translational movements. For example, rotational kinetic energy is calculated using the object’s moment of inertia and angular velocity.
Frequently Asked Questions – FAQs
Q1: What is kinetic energy?
The energy that an object possesses due to motion is known as kinetic energy.
Q2: Can kinetic energy be negative?
No, kinetic energy can’t be negative because speed squared is always a positive number, and mass can’t be negative.
Q3: When is kinetic energy highest?
Potential energy is lowest while kinetic energy is greatest. This happens when an object is moving fastest and is at its balanced position.
Q4: What happens to kinetic energy when speed decreases?
When speed decreases, kinetic energy changes into potential energy, heat, or other forms of energy.
Q5: What differentiates potential energy from kinetic energy?
The energy that an object possesses due to its position is known as potential energy. The energy that an object possesses due to motion is known as kinetic energy.
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