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47 Cards in this Set
- Front
- Back
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Inertia
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tendency of an object to resist a change in motion
Inertia depends on the objects mass. More Mass=More Inertia=Harder to Start/Stop Less Mass=Less Inertia=Easier to Start/Stop |
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Newton's First Law
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An object at rest will stay at rest and an object in motion will stay in motion until acted on by an unbalanced force.
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Force
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push or pull that can cause an object accelerate
Units-kgm/s2 Force is a vector quantity |
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Net Force
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combination of all forces that act on an object
-Symbol-<sum>F |
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Unbalanced Force
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An unequal force that changes an objects motion
(<sum>F!=0) |
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Balanced Force
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Equal forces acting on an object in opposite directions, will not cause a change in motion. (<sum>F=0)
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Two Types of Balanced Forces
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-Static/Mechanical Equilibrium: objects at rest (<sum>F=0)
-Normal Force/Support Force -Dynamic Equilibrium: object moving at constant velocity (<sum>F=00 -Moving Force=Resisting Force |
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Newton's Second Law
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Force=Mass x Acceleration
-Mass and acceleration are inversely proportional -Force and acceleration are directly proportional |
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Newton's Third Law
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For every action there is an equal but opposite reaction
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Why dont action and reaction forces cancel each other out as a balanced force?
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Forces are added together to get a balanced force only if the force is acting on the same object. Action and reaction forces are applied to different objects.
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Motion
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An object is considered in motion when its distance from another object changes
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Reference Point
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Object or place used for comparison to determine if an object is in motion
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Speed
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Distance object travels in time
Speed=Distance/Time |
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Velocity
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Speed in a given direction
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Acceleration
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Rate at which the velocity changes
(Final Velocity-Initial Velocity)/Time |
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3 types of acceleration
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Increase (positive)
Decrease (negative) Change Direction (centripetal acceleration) |
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Aristotle
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-384-322 BC
-Studied under Plato -Philosopher and scientist -Tutor to Alexander The Great -One of first to look at physical world of science -Started school called Lyceum -Natural Motion-objects natural state is rest -Unnatural Motion-force required causing motion -Heavier objects fall faster than lighter objects -Based work on observation and logic |
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Galileo
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-Late 1500s-early 1600s
-Went to University of Pisa -Dropped out which allowed him time to research physics -Started experiments with motion -Was a teacher at colleges -Became advocate of Copernicus -In 1609 was first to use telescope -In 1630s wrote a book called Dialogue -Went to jail -Went blind because he looked at the sun too much -Once an object is in motion no force is needed to keep it in motion -Force needed to change the motion of an object -Inertia-tendency of an object to resist a change in motion -All object fall at the same rate -Based work on experimentation |
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Projectile Motion
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An object upon which the only force acting on it is gravity
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Types of Projectiles
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An object dropped from rest
An object which is thrown vertically upwards An object is which thrown upwards at an angle is also a projectile |
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what are the velocities of projectiles?
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Highest velocity when released
As objects travel upward gravity slows object to 0 As object travels downward gravity increases velocity Highest velocity when object hits ground |
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What are the components of a projectile?
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The path of a projectile has a horizontal component and a vertical component.
-They are independent of each other -The projectile moves forward because of inertia -The projectile accelerates downward because of gravity |
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Work
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Work is done on an object when a force is exerted on an object that causes the object to move some distance
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What two things must be controlled in order for work to be done?
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No work without motion
No work without force in the same direction |
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Formula for work
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Work=ForceDistance
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Power
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The rate at which work is done
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Formula for power
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Power=Work/Time
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What 3 things do machines do to make work easier?
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Change the amount of force you input
Change the distance over which you exert the force Change the direction of the way you apply force |
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Why doesn't the total work change?
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If a machine allows you to apply a smaller force the distance will increase
If a machine reduces the distance the force will increase If a machine allows you to apply a force in a different direction it doesnt change how much force you have to apply or how far you move it |
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What is the mechanical advantage?
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The number of times a force exerted on a machine is multiplied by the machine
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Formula for mechanical advantage
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M.A.=Output Force÷Input Force
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What happens if M.A.>1?
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If M.A.>1 machine multiplies the input force
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What happens if M.A.<1?
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If M.A.<1 machine multiplies the input distance
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What happens if M.A.=1?
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If M.A.=1 changing direction
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Efficiency
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Compares output work to input work (%)
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Formula for efficiency
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Efficiency=Output work÷Input Work100
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Can efficiency be greater or equal to 100?
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No
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Friction
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the resistive force that opposes motion or attempted motion of an object past another with which it is in contact or through a fluid
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What 2 factors does friction depend on?
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Kinds of Surfaces
Pressure Between Surfaces Surface Area DOES NOT Affect Friction |
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3 types of friction
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Sliding
Fluid Rolling |
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Gravity
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a force that pulls objects towards the earth
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Rate of acceleration
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9.81 m/s
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Terminal velocity
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highest velocity that an object reaches
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Mass
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quantity of matter in an object
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Weight
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the gravitational force exerted on an object by the nearest most massive object
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Universal law of gravitation formula
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F(grav.)=Gm-sub1m-sub2/d-squared
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What are the 6 simple machines?
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Lever
Pulley Inclined Plane Wheel & Axel Wedge Screw |
