A force exerted by a surface on an object. Its direction is parallel to the surface, and the force is in the direction that opposes motion.
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Newton's 3rd Law
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Forces occur in pairs. The forces are equal in magnitude and opposite in direction. The forces act on different objects.
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Newton's Law of Gravitation
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The weight force between 2 objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
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normal force
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The force exerted by a surface on an object pressing against the surface. The normal force is in a direction perpendicular to the surface.
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elastic collision.
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A collision in which the colliding objects bounce off of each other. Momentum is conserved. Kinetic energy is conserved if the collision is perfectly elastic.
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momentum (p)
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The product of an object's mass and its velocity. p = mv. It can be positive or negative.
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thermal energy (Eth)
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The energy associated with the microscopic kinetic energy of the atoms that make up an object. The atoms in warmer objects vibrate at faster speeds.
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force (F)
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A push or a pull. Measured in newtons.
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Newton's 2nd Law
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a = ∑F ÷ m. Acceleration is directly proportional to net force and inversely proportional to mass.
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kinetic energy (K)
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The energy of motion. K = 1/2 • m • v^2
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weight
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A long-range force caused by the gravitational pull of the Earth (or other object) on an object.
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uniform circular motion
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Motion in a circle at constant speed. The velocity (the direction) is constantly changing and the direction of this change (the acceleration) is toward the center of the circle.
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spring energy (Us)
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The stored energy of an object due to compression or stretching. Us = 1/2 • k • ∆x^2 ( k = spring constant)
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displacement (∆x)
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The change in position of an object. Can be positive or negative.
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inelastic collision
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A collision in which the colliding objects stick together. Momentum is conserved but kinetic energy is not.
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conservation of energy
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Energy is conserved in an isolated system (initial energy = final energy). Energy can change forms.
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velocity (v)
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The rate at which an object changes its position. Can be + or -. Equal to the slope on a position vs time graph.
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impulse (J)
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The product of average force and time, also equal to the area under a F vs t curve. (J = Favg • ∆t)
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gravitational potential energy (Ug)
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The stored energy of an object due to its height. Ug = mgh
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work (W)
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Energy transfer into or out of a system due to the application of force. Work is equal to force times distance. (W = F • d)
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net force (∑F)
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The sum of all forces on an object. If ∑F = 0, then a = 0. If a = 0, then ∑F = 0. (a = ∑F ÷ m)
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distance
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The length of the path travelled by an object. Always positive.
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acceleration of an object in freefall (g)
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Near Earth's surface, free-falling objects accelerate at a rate of approximately 10 meters/second per second.
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speed (v)
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speed = distance travelled in a given time interval ÷ time interval. Always positive.
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impulse - momentum theorem
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An impulse causes a change in momentum that is equal to the impulse. (J = ∆p)
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mass (m)
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The amount of matter in an object.
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spring force
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A contact force. If an object is compressed or stretched, it can exert a force in the opposite direction.
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acceleration (a)
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The rate at which velocity changes. a = ∆v ÷ ∆t. It equals the slope on a velocity vs time graph.
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conservation of momentum
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Momentum is conserved (initial momentum = final momentum) in an isolated system.
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position (x)
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An object's location at a particular instant in time.