Transcript Forces - brightphysics

Forces
Net force ∑F is sometimes known
as total force, resultant force or
unbalanced force
Force
Force is an external influence or action
on an object that causes the object to
change velocity, to accelerate relative to
an inertial reference frame.
 Force is a vector quantity (has
magnitude and direction).

Contact versus Field

Contact Forces
Involve Physical Contact between two
objects
 Spring, pulling a wagon, kicking a ball


Field Forces
Act through empty space, do not involve
contact between two objects.
 Between two masses, between two
charges, between magnetic objects

Four types of Forces
From weakest to strongest these are:
Gravitational
 Electromagnetic
 Weak Nuclear
 Strong Nuclear

Gravitational Force – between objects
The gravitation interaction is a very
long-range interaction between particles
due to their mass. Some believe this is
caused by hypothetical objects called
gravitrons.
Electromagnetic Force –
between objects
The electromagnetic interaction is a
long range interaction between
electrically charged particles involving
the exchange of photons.
Weak (nuclear) force – arises in
certain radioactive decay processes
The weak interaction is an extremely
short-ranged interaction between subnuclear particles. The electromagnetic
and weak nuclear interactions are now
seen as a single unified interaction called
the electroweak interaction.
Strong (nuclear) force – between
subatomic particles
The strong interaction is a long-range
interaction between gluons, which
themselves consist of quarks, that binds
protons and neutrons together to form
the atomic nuclei. Some physicists think
that strong and electroweak interactions
are a single unified interaction.
Mass
The measure of an object’s inertia.
 The atomic unified mass unit (u) defined
as 1/12th the mass of the carbon-12
atom.
 1 u = 1.660540x10-27kg.

Inertial Reference Frame

If no forces act on an object, any
reference frame for which the
acceleration of the object remains zero is
an inertial reference frame.