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ALL forces are vectors. That means they have magnitude
and direction.
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There are 4 basic types of forces.
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gravitational
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electromagnetic
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strong nuclear
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weak nuclear
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Newton came up with 3 Laws of Motion.
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An object with no net (unbalanced) force acting on it will
stay at rest or will continue to move at a constant speed in a straight
line.
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When a net (unbalanced) force acts on an object, the resulting
acceleration varies directly with the force and inversely with the mass
of the object. This gives us the equations: F = ma
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Forces always exist in pairs. When one object exerts a force
on a second object, the second object exerts and equal and opposite force
on the first. This is often stated, "For every action, there is an equal
and opposite reaction."
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The weight of an object is proportional to its mass.
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Weight is the gravitational force on an object.
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If we say that gravity is the acceleration, then the force
due to gravity (weight) equals the mass of a body times gravity. This gives
us a specific form of [F = ma], which we can write as: W = mg (where
W
is weight, m is the mass, and g is gravitational acceleration
[-9.8 m/s/s for earth])
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Although gravitational mass and inertial mass are numerically
equal, they are different concepts.
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Friction - the force that acts when two objects rub
against each other
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Different substance create different amounts of friction.
Each substance has a coefficient of friction to represent how much friction
it creates. The higher the coefficient, the greater the friction. For example,
concrete has a higher coefficient than a waxed floor.
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The force due to friction is equal to the product of the
coefficient of friction times the normal force. The normal force is the
force acting perpendicular to the surface where friction is occurring.
For objects on a horizontal surface, the normal force equals the weight
of the object.
Friction Force = (coefficient of friction) X (normal
force)
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To start an object moving, you must apply a force equal to
the friction force. So, to calculate this force, simply solve for the friction
force to get the magnitude. The direction (expressed as + or -) of the
applied force will be opposite that of the friction force.
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The net force is the vector sum of all forces acting
on a body. A net force produces acceleration.
A free-falling body will continue to accelerate
(due to gravitational acceleration) until it reaches a certain terminal
velocity. This speed is attained when the downward force of gravity
equals the upward force of air resistance (drag force).
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