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### 47 Cards in this Set

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 Inertia tendency of an object to resist a change in motion Inertia depends on the objects mass. More Mass=More Inertia=Harder to Start/Stop Less Mass=Less Inertia=Easier to Start/Stop Newton's First Law An object at rest will stay at rest and an object in motion will stay in motion until acted on by an unbalanced force. Force push or pull that can cause an object accelerate Units-kgm/s2 Force is a vector quantity Net Force combination of all forces that act on an object -Symbol-F Unbalanced Force An unequal force that changes an objects motion (F!=0) Balanced Force Equal forces acting on an object in opposite directions, will not cause a change in motion. (F=0) Two Types of Balanced Forces -Static/Mechanical Equilibrium: objects at rest (F=0) -Normal Force/Support Force -Dynamic Equilibrium: object moving at constant velocity (F=00 -Moving Force=Resisting Force Newton's Second Law Force=Mass x Acceleration -Mass and acceleration are inversely proportional -Force and acceleration are directly proportional Newton's Third Law For every action there is an equal but opposite reaction Why dont action and reaction forces cancel each other out as a balanced force? 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. Motion An object is considered in motion when its distance from another object changes Reference Point Object or place used for comparison to determine if an object is in motion Speed Distance object travels in time Speed=Distance/Time Velocity Speed in a given direction Acceleration Rate at which the velocity changes (Final Velocity-Initial Velocity)/Time 3 types of acceleration Increase (positive) Decrease (negative) Change Direction (centripetal acceleration) Aristotle -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-objects natural state is rest -Unnatural Motion-force required causing motion -Heavier objects fall faster than lighter objects -Based work on observation and logic Galileo -Late 1500s-early 1600s -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 1630s 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 Projectile Motion An object upon which the only force acting on it is gravity Types of Projectiles 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 what are the velocities of projectiles? 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 What are the components of a projectile? 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 Work Work is done on an object when a force is exerted on an object that causes the object to move some distance What two things must be controlled in order for work to be done? No work without motion No work without force in the same direction Formula for work Work=ForceDistance Power The rate at which work is done Formula for power Power=Work/Time What 3 things do machines do to make work easier? 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 Why doesn't the total work change? 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 doesnt change how much force you have to apply or how far you move it What is the mechanical advantage? The number of times a force exerted on a machine is multiplied by the machine Formula for mechanical advantage M.A.=Output Force÷Input Force What happens if M.A.>1? If M.A.>1 machine multiplies the input force What happens if M.A.<1? If M.A.<1 machine multiplies the input distance What happens if M.A.=1? If M.A.=1 changing direction Efficiency Compares output work to input work (%) Formula for efficiency Efficiency=Output work÷Input Work100 Can efficiency be greater or equal to 100? No Friction the resistive force that opposes motion or attempted motion of an object past another with which it is in contact or through a fluid What 2 factors does friction depend on? Kinds of Surfaces Pressure Between Surfaces Surface Area DOES NOT Affect Friction 3 types of friction Sliding Fluid Rolling Gravity a force that pulls objects towards the earth Rate of acceleration 9.81 m/s Terminal velocity highest velocity that an object reaches Mass quantity of matter in an object Weight the gravitational force exerted on an object by the nearest most massive object Universal law of gravitation formula F(grav.)=Gm-sub1m-sub2/d-squared What are the 6 simple machines? Lever Pulley Inclined Plane Wheel & Axel Wedge Screw