S

Scalar
A quantity that possesses a magnitude but not a direction. Mass and length are common examples.
Second Law of Thermodynamics
There are a few versions of this law. One is that heat flows spontaneously from hot to cold, but not in the reverse direction. Another is that there is no such thing as a 100% efficient heat engine. A third states that the entropy, or disorder, of a system may increase but will never decrease spontaneously.
Significant digits
The number of digits that have been accurately measured. When combining several measurements in a formula, the resulting calculation can only have as many significant digits as the measurement that has the smallest number of significant digits.
Simple harmonic oscillator
An object that moves about a stable equilibrium point and experiences a restoring force that is directly proportional to the oscillator’s displacement.
Sine
In a right triangle, the sine of a given angle is the length of the side opposite the angle divided by the length of the hypotenuse.
Snell’s Law
Relates the angle of incidence to the angle of refraction: .
Sound
Waves carried by variations in air pressure. The speed of sound waves in air at room temperature and pressure is roughly 343 m/s.
Specific heat
The amount of heat of a material required to raise the temperature of either one kilogram or one gram of that material by one degree Celsius. Different units may be used depending on whether specific heat is measured in s of grams or kilograms, and joules or calories.
Spectroscope
A device that breaks incoming light down into spectral rays, so that one can see the exact wavelength constituents of the light.
Speed
A scalar quantity that tells us how fast an object is moving. It measures the rate of change in distance over time. Speed is to be contrasted with velocity in that there is no direction associated with speed.
Spring
Objects that experience oscillatory or simple harmonic motion when distorted. Their motion is described by Hooke’s Law.
Spring constant
Indicates how “bouncy” or “stiff” a spring is. More specifically, the spring constant, k, is the constant of proportionality between the restoring force exerted by the spring, and the spring’s displacement from equilibrium. The greater the value of k, more resistant the spring is to being displaced.
Standing wave
A wave that interferes with its own reflection so as to produce oscillations which stand still, rather than traveling down the length of the medium. Standing waves on a string with both ends tied down make up the harmonic series.
Static friction
The force between two surfaces that are not moving relative to one another. The force of static friction is parallel to the plane of contact between the two objects and resists the force pushing or pulling on the object.
Strong nuclear force
The force that binds protons and neutrons together in the atomic nucleus.
Sublimation
The process by which a solid turns directly into gas, because it cannot exist as a liquid at a certain pressure.
Superposition
The principle by which the displacements from different waves traveling in the same medium add up. Superposition is the basis for interference.
System
A body or set of bodies that we choose to analyze as a group.