42 Cards in this Set
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Mechanics
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The study of motion and what affects it
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Kinematics
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Description of the motion of objects
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Dynamics
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Analyzes the causes of motion.
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Scalar Quality
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one with only magnitude or size
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Is distance a scalar quality?
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Yes
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Speed
1) definition
2) is it scalar?
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1) rate at which a distance is traveled
2) yes
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Displacement
1) definition
2) is it a vector quanity?
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1) the straight line distance between two points along with the direction from the starting to the final position.
2) vector
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Vector quantity
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has both magnitude and direction
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Velocity
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vector quantity, displacement over change in time
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Instantaneous velocity
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the limit of (delta 'x'/delta 'y') as delta 't' approaches zero
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uniform motion
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motion with constant velocity (hence constant magnitude and constant direction)
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how do we determine the instantaneous velocity of a object with nonuniform motion from a graph of time vs. x?
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the derivative of that instantaneous time.
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Acceleration
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Change in velocity/change in time
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What happens if...
1) accelerate in direction of velocity?
2) accelerate in direction opposite of velocity?
3) accelerate at an angle to velocity?
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1) car speeds up
2) car slows down
3) car changes direction
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What is the definition of a free fall?
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An object only under the influence of gravity
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What is the acceleration due to gravity?
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9.80 m/s2
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Do all objects accelerate due to gravity equally?
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Yes, if you discount air resistance
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If something is thrown upward, is it considered to be in a free fall?
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yes because acceleration is the only force acting on it.
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Are the horizontal and vertical motion of an object dependent on one another?
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no! independent
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what is the shape of the trajectory of a general projectile in free fall?
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Parabolic arc
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What is a force?
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something that is capable of changing an objects state of motion, that is, changing its velocity or producing an acceleration.
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is a force a vector?
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yes
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what are the two classes of forces?
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contact forces, and action at a distance forces.
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what are the units for force?
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Newtons (kgxm/s^2)
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how do we determine net force?
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by vector addition
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what is equilibrium in terms of force?
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when net force equals zero, the vector cancel each other out and there is no change in the objects state of motion
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Newtons 1st law
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If the net force is zero, then an object at rest will remain at rest, and an object in motion will remain in motion with constant velocity unless acted on by a force
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Inertia
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The tendency of an object to resist any change in its motion. Greater for objects of larger mass
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Newtons 2nd Law
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Net force= mass x acceleration
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Is force a vector that points in the same direction as acceleration?
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yes
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Does a large force mean there will be a large acceleration?
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no, must consider mass as well
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Weight
1) is it a force?
2) are objects near earth constantly being accelerated on by gravity?
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1) yes
2) yes
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normal force
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the upward force that a surface exerts on the object that rests upon it
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Tension
1) which direction does tension go in?
2) what is tension?
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1) from the object the tension is acting on
2) a force along the length of a medium
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If a situation involves multiple objects, do we draw separate free body diagrams for them?
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yes
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What does the acronym for free body diagrams WANT F stand for?
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Weight, action, normal, tension, friction.
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Newton's Third Law
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For every force (action), there is an equal and opposite force (action)
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Why does Newton's third law not reverse newtons second law of motion?
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because newtons third law states that the action-reaction pairs act on different objects
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Can a single isolated force exist?
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no, there must be a reaction force according to Newton's third law that is equal in magnitude and opposite in direction
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What is maximum static friction equal to?
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the static friction constant multiplied by the normal force of the object. once this is equaled or exceeded, kinetic friction takes over
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Static friction
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acts to keep an object from moving. It is opposite the direction of the applied force, and is equal in magnitude
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Kinetic Friction
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acts while an object is in motion, is equal to the kinetic friction constant multiplied by the normal force acting on the object.
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PHY 103: Exam 1