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 isdirected 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.
Node
The points on a standing wave where total destructive interference causes the medium to
remain fixed at its equilibrium position.
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. As a result, the net force of
an object on the ground is zero, and the object does not move.
Nuclear fission
A nuclear reaction in which a high-energy neutron bombards a heavy, unstable atomic nucleus,
causing it to split into two smaller nuclei, and releasing some neutrons and a vast amount of
energy at the same time.
Nuclear fusion
A nuclear reaction that takes place only at very high temperatures. Two light atoms, often
hydrogen, fuse together to form a larger single atom, releasing a vast amount of energy in the
process.
Nucleus
The center of an atom, where the protons and neutrons reside. Electrons then orbit this
nucleus.
O
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).
Orbit
When an object is held in circular motion about a massive body, like a planet or a sun, due to
the force of gravity, that object is said to be in orbit. Objects in orbit are in perpetual free fall,
and so are therefore weightless.
Oscillation