Holt Physics Chapter 4 – Flashcards
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Force
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An action exerted on an object which may change the object's state of rest or motion. (Interaction which changes the motion of an object -Ex. Person hitting a baseball.) It is a vector because it has both magnitude and direction.
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SI Unit of Force
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Newton
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Contact Forces
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Forces which result from physical contact between two objects.
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Field Forces
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No physical contact between two objects. (Ex. Gravitational force or Electrical field)
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Free-body Diagram
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A diagram used to identify forces affecting the motion of a single object.
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Newtons 1st Law
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Object at rest remains at rest, object in motion stays in motion (with constant velocity) unless the object experiences a net external force.
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Inertia
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Tendency of an object to resist being moved or, if the object is moving, to resist a change in speed or direction. (Tendency of an object NOT to accelerate.)
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Ff
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The forward force.
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Fr
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Acts in the opposite direction, due to friction and air resistance.
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Fg
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The downward gravitational force.
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Net Force
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A single force whose external effects on a rigid body are the same as the effects of several actual forces action on the body. (Vector sum of all forces acting on an object.)
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Mass and Inertia
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Inertia of an object is proportional to the object's mass. (Greater mass = less acceleration)
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Equilibrium
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The state in which the net force on an object is zero. (Objects at rest or moving with constant velocity.)
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Newton's 2nd Law
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The acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to the object's mass. (Literally --> F=ma, net force = mass x acceleration)
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Newton's 3rd Law
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If two objects interact, the magnitude of the force exerted on object 1 by object 2 is equal to the magnitude of the force simultaneously exerted on object 2 by object 1, and these two forces are opposite direction.
