page_title: Stroboscope
hierarchical_section_title: Stroboscope
caption_attribution_description: English: A bouncing ball captured with a stroboscopic flash at 25 images per second. Note that the ball becomes significantly non-spherical after each bounce, especially after the first. That, along with spin and air-resistance, causes the curve swept out to deviate slightly from the expected perfect parabola. Spin also causes the angle of first bounce to be shallower than expected. As a ball falls freely under the influence of gravity, it accelerates downward, its initial potential energy converting into kinetic energy. On impact with a hard surface the ball deforms, converting the kinetic energy into elastic potential energy. As the ball springs back, the energy converts back firstly to kinetic energy and then as the ball re-gains height into potential energy. Energy losses due to inelastic deformation and air resistance cause each successive bounce to be lower than the last. The image is of a child's ball about the size of a tennis ball. Español: La imagen de una pelota rebotando fue capturada con un flash estroboscópico a 25 cuadros por segundo. Se aprecia que la pelota cambia significativamente de forma después de cada bote, especialmente luego del primero. Eso, junto a la rotación y la resistencia del aire, hace que el trayecto se desvíe ligeramente de la perfecta parábola que debería seguir. La rotación también causa que el ángulo en el primer rebote sea más profundo que lo esperado. Mientras la pelota cae libremente gracias a la fuerza de gravedad, se acelera su descenso y la energía inicial se convierte en energía potencial cinética. Al impactar superficies duras, la pelota se deforma, conviertiendo la energía cinética en energía potencial elástica. Cuando la pelota salta nuevamente, la energía se convierte otra vez en energía cinética y luego, mientras la pelota vuelve a ganar altura, la energía pasa a ser potencial. La energía se pierde debido a que la deformación inelástica y la resistencia al aire hacen que cada bote sea más bajo que el anterior. En la fotografía se muestra una pelota cuyo tamaño es similar al de una pelota de tenis. Français&#160;: Image stroboscopique (25 flashes/sec) d'un ballon rebondissant sur un sol dur. La balle perd significativement sa forme sphérique après chaque rebondissement, tout particulièrement après le premier. Ce fait, ainsi que sa rotation et la résistance de l'air, explique pourquoi la trajectoire parcourue s'écarte légèrement de la parabole parfaite prévue par la théorie. Cela explique aussi pourquoi l'angle décrit lors du premier rebond est moins fermé que prévu. Lors d'une chute libre sous l'influence de la gravité, la balle accélère, convertissant son énergie potentielle en énergie cinétique. Lors de l'impact, cette énergie est convertie en énergie potentielle élastique, qui est elle même reconvertie en énergie cinétique lors du rebond, puis en énergie potentielle au fur et à mesure que la balle s'élève à nouveau. Les pertes d'énergies dues aux déformations plastiques de la balle et au frottement avec l'air font que la balle rebondit de moins en moins haut. La balle représentée ici a la taille d'une balle de tennis.
context_page_description: A stroboscope, also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. It consists of either a rotating disk with slots or holes or a lamp such as a flashtube which produces brief repetitive flashes of light. Usually the rate of the stroboscope is adjustable to different frequencies. When a rotating or vibrating object is observed with the stroboscope at its vibration frequency, it appears stationary. Thus stroboscopes are also used to measure frequency.
  The principle is used for the study of rotating, reciprocating, oscillating or vibrating objects. Machine parts and vibrating string are common examples. A stroboscope used to set the ignition timing of internal combustion engines is called a timing light.
context_section_description: A stroboscope, also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. It consists of either a rotating disk with slots or holes or a lamp such as a flashtube which produces brief repetitive flashes of light.  Usually the rate of the stroboscope is adjustable to different frequencies.  When a rotating or vibrating object is observed with the stroboscope at its vibration frequency (or a submultiple of it), it appears stationary.  Thus stroboscopes are also used to measure frequency.
  The principle is used for the study of rotating, reciprocating, oscillating or vibrating objects.  Machine parts and vibrating string are common examples.  A stroboscope used to set the ignition timing of internal combustion engines is called a timing light.
caption: A bouncing ball captured with a stroboscopic flash at 25 images per second.
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