Name: motion energy in collisions
Uploaded: 2023-04-30T10:55:59.000Z
Duration: 1 min 18 s
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K12 Standards

Pennsylvania State Academic Standards

9-12

Physical Science

Energy

3.2.9-12.P

Kinetic Energy - I

L'energia che un oggetto possiede in virtù del suo movimento è nota come energia cinetica. Se un oggetto si muove con una velocità v, la sua energia cinetica è definita come la metà del prodotto della massa e della velocità al quadrato.
La velocità al quadrato qui è il prodotto scalare del vettore velocità con se stesso. Pertanto, l'energia cinetica è una grandezza scalare in quanto è indipendente dalla direzione del moto e dipende solo dalla velocità dell'oggetto.
La massa e la velocità al quadrato non possono mai essere negative. Quindi, l'energia cinetica posseduta da un oggetto è sempre positiva e aumenta rapidamente con l'aumentare della velocità.
Ad esempio, se due palle da bowling con masse diverse si muovono con la stessa velocità, la seconda palla da bowling, a causa della sua doppia massa, ha il doppio dell'energia cinetica.
Se la velocità della palla più leggera viene raddoppiata, la sua energia cinetica viene aumentata di quattro volte. Se la massa o la velocità di un oggetto sono trascurabili, la sua energia cinetica sarà zero.

energia cinetica – i

È plausibile supporre che maggiore sarà la velocità di un corpo, e maggiore sarà l'effetto che può avere su altri corpi. Questo non dipende dalla direzione della velocità, ma solo dalla sua grandezza. Alla fine del diciassettesimo secolo, la quantità veniva introdotta in meccanica per spiegare la collisione tra due corpi perfettamente elastici, in cui un corpo fa una collisione frontale con un altro identico ma a riposo. Quando essi si scontrano, il primo corpo si ferma, e il secondo si allontana con la velocità iniziale del primo corpo. Se hai mai giocato a biliardo o croquet, o visto un pendolo di Newton, allora avrai visto questo tipo di collisione. L'idea alla base di questa quantità era collegata alla forza che agiva su un corpo e riferita alla “energia del movimento”. Successivamente, durante il diciottesimo secolo, l'energia del movimento ha preso il nome di energia cinetica.

Tenendo a mente questo, abbiamo la definizione classica di energia cinetica. Nota che quando diciamo “classica”, intendiamo non relativistica; cioè, a velocità molto più lente di quella della luce. Per velocità equiparabili a quella della luce, la teoria della relatività richiede un'espressione diversa per l'energia cinetica di una particella.

Le unità di energia cinetica sono la massa moltiplicata per il quadrato della velocità (kg · m2/s2). Le unità di forza sono massa per l'accelerazione (kg · m/s2), così le unità di energia cinetica sono le unità di forza moltiplicate per la distanza. Queste sono le unità del lavoro, o joules.

L'energia cinetica di una particella è una singola quantità, ma l'energia cinetica di un sistema di particelle qualche volta può essere diviso in vari tipi, a seconda del sistema e del suo moto. Per esempio, se tutte le particelle in un sistema hanno la stessa velocità, il sistema sta subendo un moto traslatorio e ha energia cinetica traslazionale. Se un oggetto sta ruotando, potrebbe avere energia cinetica rotazionale. Se un oggetto sta vibrando, potrebbe avere energia cinetica vibrazionale. L'energia cinetica di un sistema, relativa ad un sistema di riferimento interno, è chiamata energia cinetica interna. Questa energia cinetica è associata al moto molecolare casuale ed è chiamata energia termica. Questi nomi saranno usati nei capitoli successivi, quando appropriati. Indipendentemente dal nome, ogni tipo di energica cinetica è la stessa quantità fisica, e rappresenta l'energia associata al movimento.

Questo testo è adattato da <a href="https://openstax.org/books/university-physics-volume-1/pages/7-2-kinetic-energy">Openstax, University Physics Volume 1, Section 7.2: Kinetic Energy.</a>

Energia cinetica – I

È plausibile supporre che maggiore è la velocità di un corpo, maggiore è l'effetto che potrebbe avere su altri corpi. Questo non dipende dal ...

Education

Didattica

JoVE Core

Physics

Fisica

Unit 1

Unità 1

Work and Kinetic Energy

Lavoro ed energia cinetica

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

motion energy in collisions

Kinetic energy is the energy of motion. It depends on how fast an object moves, not on the direction of its velocity. In classical mechanics, this idea helps explain how moving bodies affect other bodies during collisions.

A classic example is a perfectly elastic, head-on collision between two identical bodies, with one body initially at rest. After the collision, the first body stops, and the second body moves away with the first body's original velocity. This same pattern can be seen in billiards, croquet, and a Newton's cradle.

The term was first tied to the idea of the energy of motion and later named kinetic energy in the eighteenth century. Here, classical means non-relativistic, so it applies at speeds much slower than the speed of light. At speeds near the speed of light, special relativity requires a different expression for kinetic energy.

The units of kinetic energy are mass times speed squared, or kg·m²/s². These units are the same as force times distance, which are the units of work. That is why kinetic energy is measured in joules.

For a system of particles, kinetic energy can take different forms based on the motion of the system. If all the particles share the same velocity, the system has translational kinetic energy. Rotating objects can have rotational kinetic energy, and vibrating objects can have vibrational kinetic energy.

Kinetic energy can also be described relative to an internal frame of reference, where it is called internal kinetic energy. The kinetic energy linked to random molecular motion is called thermal energy. Even with different names, each type still represents energy associated with motion.

Motion Energy in Collisions

work

Work in Physics: Force and Motion

Work in physics connects force, motion, and energy transfer. Work is done when a force acts on an object and that object moves from one position to another. If there is no displacement, no work is done, even if a force is present. The amount of work depends on the force and the direction of motion. For a very small displacement, the work done is written as the dot product of force and displacement vectors. That means work depends on the size of the vectors and the angle between them. You can...

positive, negative, and zero work

How Force Direction Changes Work

Work in physics depends on the direction of a force and the way an object moves. Work is done when energy is transferred to an object. It happens when a force acts on a body that moves from one position to another. The work done by a force is defined as the integral of the force with respect to displacement along the path. Forces can change with position, and an object can move along different paths between the same two points. In vector form, the size of a force times the cosine of the angle...

energy

Energy Sources and Forms in Matter

Energy in matter comes from the Sun and changes form in many everyday processes. The universe is made of matter in different forms, and all forms of matter contain energy. On Earth, many energy sources can be traced back to the Sun, which is the ultimate energy source. Plants capture light energy from the Sun during photosynthesis and convert it into chemical energy. This stored energy can then be used in several ways. People get energy from plant foods, and wood or coal, which are fossilized...

types of potential energy

Potential Energy Examples in Everyday Physics

Potential energy is stored energy, and it appears in several everyday forms. It is also called energy at rest because it is ready to be used later. In physics, different systems can store energy in different ways. Gravitational potential energy is the energy stored by an object because of its position. An apple hanging from a tree is one clear example. Electrical potential energy is stored when electric charges attract or repel each other. Chemical potential energy is stored in the bonds...

types of kinetic energy

How Mass and Speed Affect Kinetic Energy

Kinetic energy depends on an object’s mass and speed. A heavier object moving at the same speed has more kinetic energy than a lighter one. An object moving faster also has more kinetic energy when the mass stays the same. The transcript also describes several forms of kinetic energy. Mechanical energy is linked to the motion of an object. A bullet fired from a gun and water flowing down a dam are examples of mechanical energy. Electrical energy comes from the flow of electric charges.

kinetic energy - i

Kinetic energy is the energy of motion. It depends on how fast an object moves, not on the direction of its velocity. In classical mechanics, this idea helps explain how moving bodies affect other bodies during collisions. A classic example is a perfectly elastic, head-on collision between two identical bodies, with one body initially at rest. After the collision, the first body stops, and the second body moves away with the first body's original velocity. This same pattern can be seen in...

kinetic energy - ii

Kinetic Energy, Momentum, and Reference Frames

Kinetic energy depends on mass, speed, momentum, and the frame of reference. For a particle, it is one-half of the particle’s mass times the square of its speed. The same idea can also be written in terms of mass and momentum instead of mass and velocity. The units of kinetic energy are mass times speed-squared. These units match the units of work. Force times distance also gives the same units, so kinetic energy and work are measured in joules. That is why work and kinetic energy are two...

work-energy theorem

Work Done and Kinetic Energy

Work done by the net force is linked to an object's kinetic energy. In physics, the net force is the total force acting on an object. Kinetic energy is the energy of motion. The work-energy theorem states that the work done by all forces on an object equals the change in its kinetic energy. This relationship is useful when acceleration is not constant. If the change in velocity is known, the theorem can still help calculate the work done by a force. It connects force, motion, and energy in a...

work and energy for variable forces

Variable Force Work via Graphs and Energy

Variable force work and energy can be found by using force-displacement graphs and the work-energy principle. When a force changes as an object moves, the calculation is more complex than for a constant force. Work is the product of force and displacement, and energy is the capacity of a system to do work. For a constant force, work is found by multiplying the force by the distance moved in the direction of the force. For a variable force, the work done is the area under the force-displacement...

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work-energy theorem for motion along a curve

work-energy-theorem-for-motion-along-a-curve

Work-Energy Along Curved Paths

The work-energy theorem can be applied to motion along a curved path. A curved path can be treated as many tiny straight paths added together. On each small part, the force can be taken as constant, so the work-energy theorem can be used there. The total result comes from adding the work done along all of those small path segments. The net work is found with an integral, which adds the work from each infinitesimal path. The total change in kinetic energy is the sum of the changes along the way.

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work done over an inclined plane

Gravity and Work on Sloped Motion

Gravity and work on sloped motion can be described with the center-of-mass framework. For a rigid body, internal forces do no work, so they can be ignored. The work-energy theorem then uses only the external forces. The work done by gravity depends on the path of the body’s center of mass. If gravity helps increase kinetic energy, the work is positive. If an object is lifted against gravity, the work is negative because kinetic energy decreases. For horizontal motion, the work done by or...

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work done by many forces

Calculating Work from Multiple Forces

Calculating work from multiple forces can be done in two ways, and both methods give the same result. One method finds the work done by each force first. The other method finds the net force by adding the force vectors first.

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work done by gravity

Gravity and Positive vs Negative Work

Gravity is one of the four fundamental forces in nature. On Earth, the force between an object and Earth is called gravity. Gravity does work on an object when it moves the object toward Earth’s center. In that case, the work done by gravity is positive. When an external force lifts an object away from Earth’s center, that force works against gravity. The net work done in this case is negative. If an object moves along the Earth with no change in distance toward or away from Earth’s center,...

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power

Power in Work and Motion

Power connects work with the time needed to do it. Work depends on force and displacement. The work-energy theorem also links net work on an object to the change in its kinetic energy between two points on its path. These ideas do not include time directly, but time still matters in many real situations. A sprinter is a clear example. Two runners may reach the same finish speed, so they do the same amount of work. The winner is the one who reaches that speed in less time. Power describes this...

power expended by a constant force

Power as the Rate of Doing Work

Power describes how fast work is done. In physics, two sprinters can cross the finish line with the same velocity and do the same amount of work, but the one who finishes first has greater power because the work takes less time. Average power is the work done during a time interval divided by that time interval. When the time interval becomes very small, this becomes instantaneous power. That gives the power at a specific moment instead of over a longer stretch of time. Power can also be...

key terms and concepts

Learn how kinetic energy explains collisions, motion, and energy units. See examples like billiards, Newton's cradle, rotation, vibration, and thermal energy.

Motion Energy in Collisions | JoVE K12

physics

JoVE Core Physics introduces the theory and application of fundamental physics topics, including kinematics, dynamics, fluid mechanics, statics, waves, and acoustics, with concise and easy-to-understand animated videos. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

3.2.9-12.Q

Louisiana Student Standards for Science

High School

HS-PS3-2

HS-PS3-3

HS-PS3-1

Tennessee Academic Standards

PHYS.PS3.1

Minnesota Academic Standards in Science

2.2.1 9P.2.2.1.1

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New Jersey Student Learning Standards for Science

Arizona Science Standards

HS+Phy.P4

HS+Phy.P4U1.6

Next Generation Science Standards

Florida Department of Education

SC.912.P.10

SC.912.P.10.1

SC.912.P.12

SC.912.P.12.9

Texas Essential Knowledge and Skills

PHYS.7

PHYS.7.B

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South Carolina College and Career Ready Science Standards

P-PS3-1

P-PS3-2

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New York State Science Learning Standards

HS. Energy

HS-PS3-1.

Georgia Standards of Excellence

SP3.

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3.2.9-12.O

Types of Potential Energy

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Kinetic Energy - II

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Gravitational Potential Energy

Potential energy is not just a property of each object, but also a property of the interactions between objects in a chosen system. For each type of ...

Elastic Potential Energy

Elastic potential energy is the energy stored as a result of the deformation of an elastic object, such as the stretching of a spring. An object is ...

Energy in Simple Harmonic Motion

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Kinetic and Potential Energy of a Wave

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Energy and Power of a Wave

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Energy Carried By Electromagnetic Waves

Anyone who has used a microwave oven knows there is energy in electromagnetic waves. Sometimes, this energy is obvious, such as in the summer sun&#39;s ...

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Energy Transfer in Chemical Reactions

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Students who demonstrate understanding can plan and conduct an investigation to provide evidence that the transfer of thermal energy when two components of different temperature are combined within a closed system results in a more uniform energy distribution among the components in the system (second law of thermodynamics). Clarifying Statement: Emphasis is on analyzing data from student investigations and using mathematical thinking to describe the energy changes both quantitatively and conceptually. Examples of investigations could include mixing liquids at different initial temperatures or adding objects at different temperatures to water. Assessment Boundry: Assessment is limited to investigations based on materials and tools provided to students.

3.2.9-12.R

force-and-potential-energy-in-one-dimension

Force and Potential Energy in One Dimension

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force-and-potential-energy-in-three-dimensions

Force and Potential Energy in Three Dimensions

Consider a particle moving under the action of a conservative force that has components along each coordinate axis. Each component of force is a function ...

Energy Diagrams - I

The dynamics of a mechanical system can be easily understood by interpreting a potential energy diagram. Since energy is a scalar quantity, the ...

Energy Diagrams - II

Energy diagrams are important to understand the dynamics of a system. The topology of an energy diagram helps illustrate the equilibrium points of the ...

Students who demonstrate understanding can develop and use a model of two objects interacting through electric or magnetic fields to illustrate the forces between objects and the changes in energy of the objects due to the interaction. Clarifying Statement: Examples of models could include drawings, diagrams, and texts, such as drawings of what happens when two charges of opposite polarity are near each other. Assessment Boundry: Assessment is limited to systems containing two objects.

3.2.9-12.S

Motion Energy in Collisions

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