# Dynamics and Kinematics Roy Johnson
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Force formula

F = ma
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dynamics

the description of *what* causes things to move
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kinematics

the description of *how* things move; measures the positions, speed or velocity, and acceleration of objects
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vector

a measurable quantity that has both a scalar value *and* a direction associated with it
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scalar

any measurable quantity that can be completely described with a single piece of information; can be positive, negative, or zero
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displacement

change in position that involves a distance *and* a direction
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distance

a positive scalar quantity; no direction associated with it
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speed

the rate of motion; scalar quantity
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rate

compares the change in the value of a quantity to a certain span of time
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speed formula

V = d/Δt
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average speed

total distance divided by the total time
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velocity

rate of displacement; vector quantity
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acceleration

rate of change of the speed or velocity during a given time interval
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acceleration formula

a = Δv/Δt
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force

a push or a pull on a system
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force vector

*F*
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unit of force

newton (N)
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newton

1 kg*m/s2
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contact forces

act only when one system touches another; caused by the attraction or repulsion of atom-sized particles; a.k.a. mechanical forces
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field force

acts between the objects that are not touching; matter is not needed to transmit them; \”action-at-a-distance\” force
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weight

the gravitational attraction exerted on an object’s mass by the earth
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proportionality constant

9.81 N/kg
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inertia

the property of a body by which it remains at rest or continues moving in a straight line unless acted upon by a directional force
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Law of Inertia/Newton’s First Law

An object will not move by itself and that, once in motion, it won’t stop unless some force acts upon it
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Law of Accelerated Motion/Newton’s Second Law

When you push an object with more force, it will move faster and farther away.
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Law of Action-Reaction/Newton’s Third Law

For every action, there is an equal but opposite reaction.
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normal

\”perpendicular to\”
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friction

a contact force that opposes the movement of objects past each other
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gravity

a basic property of all matter; depends on the masses of the two objects and the distance between their centers
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law of universal gravitation

Simply: if you double one of the masses, you double the gravitational force
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air resistance

friction on an object moving through the air
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free fall

objects that fall due to gravity alone (no other forces are acting upon it whatsoever)
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gravitational acceleration

9.81 m/s2
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weight formula

w = mg
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terminal velocity

the constant velocity of an object’s fall
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momentum

a property that determines how much force is required to change their motion; vector quantity; has magnitude and direction
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momentum formula

*p* = m*v*
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linear momentum

momentum of a system moving in a straight path
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angular momentum

momentum of a rotating object; depends on the mass of the system, how fast it is rotating, and the distance of its mass from the axis of rotation
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impulsive forces

considered to act during short periods of time and being much larger than the other forces acting on a system
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conservation of momentum