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| scale
— (1) relative size of things, as in large scale versus small scale; (2) association between representation on a drawing or model and the real parameter being represented, such as 1 cm = 1 N on a force diagram. scattering — absorption of light by matter followed by emission of light in random directions. Scattering is done by atoms or materials with particle sizes that are small compared to the wavelength of the light. scientific method — rigorous method of developing and testing knowledge by comparing hypotheses against objective observational evidence. scientific notation — method of writing numbers that uses a coefficient multiplied by a power of 10. For example, the number 1,500 is written in scientific notation as 1.5×103. screw — device consisting of a spirally grooved body and grooved head that converts rotational motion into translational motion. One of six types of simple machines. A screw is often used to fasten two materials together. second law of thermodynamics — heat only flows spontaneously in nature from hotter to colder objects. Alternately stated that processes occur in nature in a manner that maintains or increases entropy. The implication of the second law is that heat cannot be transferred from a colder object to a hotter object without external work being done on the system. series circuit — electric circuit where the electric current has only one path. short circuit — electric circuit where the resistance is very low or near zero, resulting in high current flow that exceeds the circuit’s design limits and can damage the components. significant figures — those digits in a number that carry meaning as to the precision of the number or the measurement of it. Leading zeroes (the zeroes on the left of the first digit) are not significant because they are placeholders that indicate the scale of the number or measurement. simple machine — mechanical device that uses only one kind of motion to change the magnitude or direction of a force. The six kinds of simple machines are lever, pulley, wheel and axle, ramp, wedge, and screw. | sliding friction
— friction force between two surfaces that are moving relative to each other through sliding. Also called kinetic friction. slope — ratio of the increase in the vertical or y-direction divided by the change in the horizontal or x-direction. Snell’s law of refraction — ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant. The value of the constant is the ratio of the indices of refraction for the two materials. solenoid — coil of wire, usually cylindrical, that uses electric current to create a magnetic field. solid — phase of matter that does not flow but instead holds its shape and volume, because its particle’s energies are insufficient to break intermolecular bonds. specific heat — amount of energy it takes to change the temperature of one unit of mass by one degree. Measured in joule per kilogram per degree Celsius (J kg−1 °C−1) or joule per gram per degree Celsius (J g−1 °C−1). Also called specific heat capacity. spectral line — individual wavelength of light that is emitted or absorbed by a material as viewed in a spectrograph. spectrogram — three-variable graphic representation of sound that plots time on the horizontal axis, frequency on the vertical axis, and amplitude as different colors. spectrograph — scientific instrument that disperses light into its different wavelengths (or colors). A simple example of a spectrograph is a glass prism. Also called a spectrometer or spectroscope. spectrum — characteristic wavelengths of light emitted or absorbed by an object. specular reflection — reflection of light off smooth or shiny surfaces that produces a visible image of the object. Light striking a mirror is an example of specular reflection. speed — ratio of distance traveled to the time taken, or distance divided by time. Speed is also the magnitude of the velocity vector and therefore cannot be negative. | |||||||||||||
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