Name: energy conservation in simple harmonic motion
Uploaded: 2023-05-16T08:18:41.000Z
Duration: 1 min 17 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Physical Science

Energy

3.2.9-12.P

problem-solving-energy-in-simple-harmonic-motion

Problem Solving: Energy in Simple Harmonic Motion

Imaginons qu’une voiture se déplace sur une route cahoteuse. Ici, la suspension de la voiture agit comme un ressort reliant la masse de la voiture aux roues.
Au cours de son mouvement, le ressort se comprime et se dilate, exécutant un mouvement harmonique simple.
Supposons que la voiture rebondisse avec une certaine amplitude ; quelle est sa vitesse maximale, et comment son énergie totale change-t-elle si elle est à mi-chemin entre sa position initiale et sa position d’équilibre ?
L’énergie totale dans le mouvement harmonique simple reste conservée. Le réarrangement des termes donne la vitesse à n’importe quelle position pendant le mouvement.
La vitesse maximale se produit lorsque le ressort de la voiture passe en position d'équilibre. En substituant les quantités connues, on obtient la vitesse maximale. L’énergie totale en position d’équilibre est alors obtenue en substituant les quantités connues et calculées.
Lorsque le ressort de la voiture se déplace de l'amplitude maximale à la moitié de l'amplitude, la vitesse est considérée comme négative. L’énergie totale est calculée en remplaçant la vitesse par d’autres quantités connues.
Dans les deux cas, l’énergie totale d’un mouvement harmonique simple est la même.

<ol>
	<li>Young, H.D. et Freedman, R.A. (2012). La physique universitaire avec la physique moderne. San Francisco, Californie : Pearson. p.446.</li>
	<li>OpenStax. (2019). Physique universitaire Vol. 1. [Version Web]. P. 754. Récupéré de <a href="https://openstax.org/books/university-physics-volume-1/pages/15-2-energy-in-simple-harmonic-motion">https://openstax.org/books/university-physics-volume-1/pages/15-2-energy-in-simple-harmonic-motion</a></li>
</ol>

résolution de problèmes : Énergie en mouvement harmonique simple

Le mouvement harmonique simple (MHS) est un type de mouvement périodique dans le temps et dans la position, dans lequel un objet oscille d'avant en arrière autour d'une position d'équilibre avec une amplitude et une fréquence constantes. Dans le MHS, il y a un échange continu entre l'énergie potentielle et l'énergie cinétique, ce qui entraîne l'oscillation de l'objet.

Considérons le ressort d'un amortisseur de voiture. Le ressort attaché à la roue effectue un mouvement harmonique simple tandis que la voiture se déplace sur une route cahoteuse. La force exercée sur le ressort est conservatrice et l'énergie potentielle est stockée lorsque le ressort est étiré ou comprimé. Dans ce cas, la roue attachée au ressort oscille dans une dimension, avec la force du ressort agissant parallèlement au mouvement. À la position d'équilibre, l'énergie potentielle stockée dans le ressort est nulle. S'il n'y a pas de forces dissipatives, l'énergie totale est la somme de l'énergie potentielle et de l'énergie cinétique et s'exprime comme suit :

<img alt="Equation1" src="/files/ftp_upload/14743/14743_Equation_1.svg" style="text-align: center; height: 35px;" />

La totalité de l'énergie dans le mouvement harmonique simple reste conservée pour le système à chaque point pendant le mouvement et est proportionnelle au carré de l'amplitude.

L'équation d'énergie totale dans le mouvement harmonique simple présente une relation utile entre la vélocité, la position et l'énergie mécanique totale. Cette équation peut être utilisée si le problème nécessite une relation entre la position, la vélocité et l'accélération sans faire référence au temps. Étant donné que l'équation de conservation d'énergie implique le déplacement et la vélocité, il faut déduire les signes du déplacement et de la vélocité de la situation. Par exemple, si le corps se déplace de la position d'équilibre vers le point de plus grand déplacement positif, le déplacement et la vélocité sont positifs.

L'étude de l'énergie dans le mouvement harmonique simple est essentielle pour comprendre le comportement des systèmes oscillants en physique et en ingénierie.

Résolution de problèmes : Énergie en mouvement harmonique simple

Le mouvement harmonique simple (SHM) est un type de mouvement périodique dans le temps et la position, dans lequel un objet oscille d’avant en arrière autour d’un équilibre ...

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Education

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KEY TERMS AND CONCEPTS

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energy conservation in simple harmonic motion

Energy conservation in simple harmonic motion explains how a spring and mass system shares energy as it moves back and forth around equilibrium. Simple harmonic motion, or SHM, is periodic motion in time and position. The object oscillates with a constant amplitude and frequency.

In SHM, kinetic energy and potential energy change into each other continuously. A good example is the spring in a car shock absorber as the car moves on a bumpy road. The wheel attached to the spring oscillates in one dimension, and the spring force acts parallel to the motion. The force is conservative, so energy is stored as potential energy when the spring is stretched or compressed.

At the equilibrium position, the spring’s potential energy is zero. If no dissipative forces are present, the total mechanical energy stays constant throughout the motion. This total energy is the sum of kinetic energy and potential energy. In SHM, it is also proportional to the square of the amplitude.

The total energy equation in SHM links position, velocity, and mechanical energy. It is useful when a problem asks for a connection between position, velocity, and acceleration without using time. Because the equation includes displacement and velocity, the signs must be inferred from the motion. For example, if the object moves from equilibrium toward the greatest positive displacement, both displacement and velocity are positive.

Understanding energy in simple harmonic motion helps explain how oscillating systems behave in physics and engineering.

Energy Conservation in Simple Harmonic Motion

energy-conservation-in-simple-harmonic-motion

simple harmonic motion

Period and Frequency in Simple Harmonic Motion

Simple harmonic motion describes oscillatory motion when the net force follows Hooke's law. In this type of motion, the force acts toward the equilibrium position. If there is no damping from friction or other non-conservative forces, the oscillator moves with equal displacement on both sides of equilibrium. The period of a simple harmonic oscillator is found from the equation of motion. Period is the time for one complete oscillation. Frequency is the inverse of period, so the two values can...

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characteristics of simple harmonic motion

characteristics-of-simple-harmonic-motion

Simple Harmonic Motion: Period and Phase

Simple harmonic motion depends on how displacement, force, and acceleration work together. In this motion, the acceleration of the system, and therefore the net force, is proportional to the displacement and points in the opposite direction. That restoring force pulls the object back toward equilibrium. The period and frequency of a simple harmonic oscillator do not depend on amplitude. A diving board shows this idea well. A stiff, thick diving board has a large force constant, so it has a...

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oscillations about an equilibrium position

oscillations-about-an-equilibrium-position

Stable Equilibrium and Atomic Oscillation

Stable equilibrium is a key idea in oscillation. When an object sits at a stable equilibrium point, a small push moves it away, but it then tends to oscillate around that point. If the equilibrium point is unstable, a slight disturbance will not bring the object back. The transcript also describes a half-stable equilibrium point. It is still considered unstable, but the name comes from the fact that the force on only one side points toward the equilibrium point. That makes it different from a...

energy in simple harmonic motion

Simple Harmonic Motion: Energy and Speed

Simple harmonic motion combines potential energy and kinetic energy. In a spring-like oscillator, Hooke’s law explains the potential energy stored when the string or spring is stretched or compressed. Because there are no dissipative forces, the object also has kinetic energy as it moves.

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frequency of spring-mass system

How Mass and Spring Stiffness Set Oscillation

A spring-mass system shows simple harmonic motion, and its oscillation rate depends on the mass and the spring force constant. In this model, the angular frequency, period, and frequency are set by those two values. They do not depend on the motion’s amplitude or on the initial conditions. To find these relationships, the system can be analyzed with Newton’s second law. Imagine a block on a spring on a frictionless surface. Three forces act on the mass: weight, the normal force, and the spring...

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simple harmonic motion and uniform circular motion

simple-harmonic-motion-and-uniform-circular-motion

Simple Harmonic Motion from Circular Motion

Simple harmonic motion and uniform circular motion are closely linked. Simple harmonic motion is oscillatory motion in a system where the net force follows Hooke’s law. Uniform circular motion is motion along a circular path at constant speed. A simple way to create simple harmonic motion is to use uniform circular motion. One example is a ball attached to a vertical turntable that spins at a steady rate. If you watch the ball’s shadow on the floor, the shadow, or projection, moves in simple...

problem solving: energy in simple harmonic motion

Energy conservation in simple harmonic motion explains how a spring and mass system shares energy as it moves back and forth around equilibrium. Simple harmonic motion, or SHM, is periodic motion in time and position. The object oscillates with a constant amplitude and frequency. In SHM, kinetic energy and potential energy change into each other continuously. A good example is the spring in a car shock absorber as the car moves on a bumpy road. The wheel attached to the spring oscillates in...

simple pendulum

Pendulum Motion and Period

A simple pendulum is a small ball, or bob, hanging from a string that has negligible mass and does not stretch. Pendulums appear in everyday life, including clocks, swing sets, and a sinker on a fishing line. Their motion is a useful model for studying repeating movement. The period of a simple pendulum depends on two factors: its length and the acceleration due to gravity. The period does not depend on the bob’s mass or on the maximum displacement. For small angles, the pendulum behaves like...

torsional pendulum

Angular Oscillation in a Torsion String

Angular oscillation in a torsion string is shown by a rigid body suspended from a string that twists as it moves. The twisting of the string provides the restoring force. The string is ideally massless, and in practice its mass is much smaller than the rigid body&amp;#39;s mass, so it is neglected. When the angular displacement is small, the motion can be modeled as linear angular oscillation. The amplitude is measured as an angle. In this system, the role of mass is played by the rigid...

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physical pendulum

Physical Pendulum Motion and Inertia

A physical pendulum is a rigid body that hangs from a fixed pivot point and swings when it is displaced. Its motion is similar to a simple pendulum. To describe that motion, physicists use the small-angle approximation, where sin θ ≈ θ. This approximation is valid up to about 14°. The period and angular frequency of a physical pendulum can be found by comparing it with a spring-mass system. The mass moment of inertia is the key quantity that describes how the body’s mass is spread around the...

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measuring acceleration due to gravity

Using Pendulums to Find Gravity

Pendulums can be used to measure the acceleration due to gravity. A simple pendulum is a point mass attached to a string. A physical pendulum is an object that swings in a similar way, but its mass is spread out, so it cannot be treated as a point mass on a string. A physical pendulum is described using rotational motion and moment of inertia. In both types of pendulum, gravity provides the restoring force that brings the object back toward the middle of its swing. For a simple pendulum,...

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damped oscillations

Energy Loss in Oscillations

Oscillations in the real world often lose energy as they move. A system that keeps the same amplitude without any loss is called undamped. That kind of motion is rare, because friction and other non-conservative forces usually reduce the motion over time. Common examples show this clearly. A guitar string stops vibrating a few seconds after it is plucked. A swing also needs a person to keep pushing it if the motion is to continue. In some devices, such as car shock absorbers, damping is useful...

types of damping

How Damping Changes Oscillations

Damping changes how a system oscillates by reducing its back-and-forth motion. As damping increases, the period and frequency begin to change because damping opposes motion and lowers the net force in both directions. When damping is very large, the system stops oscillating altogether. It then moves slowly toward equilibrium. An overdamped system reaches equilibrium slowly. An underdamped system reaches equilibrium faster, but it oscillates around the equilibrium point while doing so. A...

forced oscillations

Resonance in Driven Oscillators

Resonance in driven oscillators describes how a periodic force changes an object’s motion. A driven oscillator may first move in a messy way. These early motions are called transients. After the transients die out, the oscillator reaches a steady state. In this state, the motion becomes periodic and the displacement is determined. The amplitude of a driven oscillator can be found from the equations for force and motion. That amplitude depends on the natural frequency of the system and the...

concept of resonance and its characteristics

concept-of-resonance-and-its-characteristics

Resonance in Music, Cars, and Radios

Resonance is a key feature of driven oscillators, and it depends strongly on damping. Damping is the process that reduces motion by removing energy from the system. When a system must resonate at one specific frequency, very light damping is needed. Piano strings and many other musical instruments are common examples of this kind of response. Heavy damping works better when the goal is small-amplitude oscillations. A car suspension system uses this approach so that bumps do not produce large...

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key terms and concepts

Learn how kinetic and potential energy change in simple harmonic motion, with a spring example and the energy equation used to solve SHM problems.

Energy Conservation in Simple Harmonic Motion | JoVE K12

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3.2.9-12.O

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3.2.9-12.R

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3.2.9-12.S

Energy Conservation in Simple Harmonic Motion

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