Newton’s Law of Universal Gravitation

The force of gravity, F, between two particles of mass and , separated by a distance r, has a magnitude of , where G is the gravitational constant. The force is directed along the line joining the two particles.

Newton’s Second Law

F = ma. The net force, F, acting on an object causes the object to accelerate, a. The magnitude of the acceleration is directly proportional to the net force on the object and inversely proportional to the mass, m, of the object.

Newton’s Third Law

To every action, there is an equal and opposite reaction. If an object A exerts a force on another object B, B will exert on A a force equal in magnitude and opposite in direction to the force exerted by A.

Normal

The line perpendicular to a surface. There is only one normal for any given surface.

Normal force

The reaction force of the ground, a table, etc., when an object is placed upon it. The normal force is a direct consequence of                Newton’s Third Law: when an object is placed on the ground, the ground pushes back with the same force that it is pushed upon. уаауа

As a result, the net force of an object on the ground is zero, and the object does not move.

Nucleus

The center of an atom, where the protons and neutrons reside. Electrons then orbit this nucleus.

Optics

The study of the properties of visible light, i.e., the portion of the electromagnetic spectrum with wavelengths between 360 and 780 nm (1 nm = m/s).

Pascals

The unit for measuring pressure. One Pascal is equal to one Newton per meter squared, 1 Pa = 1 N/m².

Pendulum

A pendulum consists of a bob connected to a rod or rope. At small angles, a pendulum’s motion approximates simple harmonic motion as it swings back and forth without friction.

Period

The time it takes a system to pass through one cycle of its repetitive motion. The period, T, is the inverse of the motion’s frequency, f = 1/T.

Photon

A small particle-like bundle of electromagnetic radiation.

Power

Defined as the rate at which work is done, or the rate at which energy is transformed. P is measured in joules per second (J/s), or watts (W).

Pressure

A measure of force per unit area. Pressure is measured in N/m² or Pa.

Proton

A positively charged particle that, along with the neutron, occupies the nucleus of the atom.

Pulley

A pulley is a simple machine that consists of a rope that slides around a disk or block.

Quark

The building blocks of all matter, quarks are the constituent parts of protons, neutrons, and mesons.

Radian

A unit for measuring angles; also called a “rad.” 2π rad = 360º.

Radioactivity

An object is called radioactive if it undergoes radioactive decay.

Reflect

A wave on a string that is tied to a pole at one end will reflect back toward its source, producing a wave that is the mirror-image of the original and which travels in the opposite direction.

Refraction

The bending of light as it passes from one medium to another. Light refracts toward the normal when going from a less dense medium into a denser medium and away from the normal when going from a denser medium into a less dense medium.

Right-hand rule

A means of defining the direction of the cross product vector. To define the direction of the vector , position your right hand so that your fingers point in the direction of A, and then curl them around so that they point in the direction of B. The direction of your thumb shows the direction of the cross product vector.

Rigid body

An object that retains its overall shape, meaning that the particles that make up the rigid body stay in the same position relative to one another.

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