sat物理常用术语词汇：F

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F

Faraday’s Law

A law, | | = , which states that the induced emf is the change in magnetic flux in a certain time.

First Law of Thermodynamics

Essentially a restatement of energy conservation, it states that the change in the internal energy of a system is equal to the heat added plus the work done on the system.

Focal length

The distance between the focal point and the vertex of a mirror or lens. For concave mirrors and convex lenses, this number is positive. For convex mirrors and concave lenses, this number is negative.

Focal point

The point of a mirror or lens where all light that runs parallel to the principal axis will be focused. Concave mirrors and convex lenses are designed to focus light into the focal point. Convex mirrors and concave lenses focus light away from the focal point.

Force

A push or a pull that causes an object to accelerate.

Free-body diagram

Illustrates the forces acting on an object, drawn as vectors originating from the center of the object.

Frequency

The number of cycles executed by a system in one second. Frequency is the inverse of period, f = 1/T. Frequency is measured in hertz, Hz.

Frictional force

A force caused by the roughness of two materials in contact, deformations in the materials, and a molecular attraction between the materials. Frictional forces are always parallel to the plane of contact between two surfaces and opposite the direction that the object is being pushed or pulled.

Fundamental

The standing wave with the lowest frequency that is supported by a string with both ends tied down is called the fundamental, or resonance, of the string. The wavelength of the fundamental is twice the length of the string