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PASS Content Standard 2.1 Objects change their motion only when a net force is applied. Laws of motion are used to determine the effects of forces on the motion of objects.

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Motion - 12 min

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Earth rotates on its axis at 1,100 mph Earth orbits the Sun at 68,000 mph

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The whole galaxy rotates at 490,000 mph

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Two Dimensional World

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Speed= distance time

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Speed= distance time A snail crawls 10 feet in 5 minutes. What is the speed of the snail? = 10 feet 5 minutes =2 feet/min

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Average speed= total distance total time

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Average speed= total distance total time A boy runs 1 mile in 6 minutes, rests for 2 minutes, then walks 1 mile in 12 minutes. What is his average speed? = 1 mile + 1 mile 20 minutes = 2 miles 20 minutes

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Distance (meters) Time (seconds)

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is a vector quantity because it has both speed and direction.

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Vectors - 12 min

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All these planes have the same speed. How is their velocity different?

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The length of the line represents the quantity (speed) and the arrow indicates the direction. Add vectors head to tail.

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Direction is indicated by compass degrees

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The magnitude of the speed is indicated by the measured length (scale) of the line.

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0o0o 90 o 180 o 270 o An airplane is flying 200 mph at 50 o. Wind velocity is 50 mph at 270 o. What is the velocity of the plane?

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0o0o 90 o 180 o 270 o

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0o0o 90 o 180 o 270 o

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0o0o 90 o 180 o 270 o

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0o0o 90 o 180 o 270 o

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0o0o 90 o 180 o 270 o

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Acceleration = Velocity (final) - Velocity (original) time

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A car traveling at 60 mph accelerates to 90 mph in 3 seconds. What is the car’s acceleration?

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Acceleration = Velocity (final) - Velocity (original) time A car traveling at 60 mph accelerates to 90 mph in 3 seconds. What is the car’s acceleration? = 90 mph - 60 mph 3 seconds = 30 mph 3 seconds = 10 mph/second

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A car traveling at 60 mph slams on the breaks to avoid hitting a deer. The car comes to a safe stop 6 seconds after applying the breaks. What is the car’s acceleration?

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Acceleration = Velocity (final) - Velocity (original) time A car traveling at 60 mph slams on the breaks to avoid hitting a deer. The car comes to a safe stop 6 seconds after applying the breaks. What is the car’s acceleration? = 0 mph - 60 mph 6 seconds = - 60 mph 6 seconds = - 10 miles per hour per second

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Acceleration toward the center of a circular path.

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For an object to travel in a curved path, some force must be accelerating it toward the center of the circle.

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Force provided by engine Acceleration provided by tires

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What happens if the accelerating force is removed?

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The object moves in a straight line.

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An apparent force that appears only in rotating frames of reference.

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This “false” force appears to push away from the center of the circular path.

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If you are riding in the passenger seat of this car, what do you feel?

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What's actually happening?

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Aristotle and Newton had different ideas about forces and motion. Aristotle's idea: For an object to move at a constant speed, a constant force must be applied. Newton's idea: An object moving at a constant speed will continue at that speed without additional force being applied.

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Produce NO Motion

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Produce Motion

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Sliding - two solid surfaces rubbing against each other. Rolling - an object rolling over a surface. Fluid - an object moving through a fluid.

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Newton’s Laws - 5 min

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An object at rest will remain at rest, and a moving object will remain at a constant velocity unless acted on by unbalanced forces.

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Force = mass X acceleration F = Ma

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For every action, there is an equal and opposite reaction.

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Rockets - 6 min

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Momentum - 8 min

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Does a long pendulum swing faster than a short one?

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Does a heavy pendulum swing faster than a light one?

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The total momentum of any group of objects remains the same unless acted on by outside forces.

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Elastic - occur when both momentum and kinetic energy are conserved. Inelastic - occur when momentum is conserved, but kinetic energy is not.

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M 1 V 1 = M 2 V 2 Before After

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Colliding objects have same mass Elastic Collision

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Heavy object strikes light object Elastic Collision

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Light object strikes heavy object Elastic Collision

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Inelastic Collision Colliding objects have same mass

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Rollercoasters - 4 min

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Units of Force are Newtons Units of Distance are Meters Newton Meters = Joules

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Work - 2 min

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A force of 200 Newtons is used to move an object 10 meters. How much work is done?

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A force of 200 Newtons is used to move an object 10 meters. How much work is done? W = Fd

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A force of 200 Newtons is used to move an object 10 meters. How much work is done? W = Fd = (200 N)

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A force of 200 Newtons is used to move an object 10 meters. How much work is done? W = Fd = (200 N)(10 meters)

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A force of 200 Newtons is used to move an object 10 meters. How much work is done? W = Fd = (200 N)(10 meters) = 2000 Joules

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Units of Work are Joules Joules per second = Watts Power is the rate at which work is done.

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power - 2 min

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A machine produces 250 joules of work in 2 seconds. How much power is produced?

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A machine produces 250 joules of work in 2 seconds. How much power is produced? P = W / t

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A machine produces 250 joules of work in 2 seconds. How much power is produced? P = W / t = (250 joules)

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A machine produces 250 joules of work in 2 seconds. How much power is produced? P = W / t = (250 joules) / 2 sec

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A machine produces 250 joules of work in 2 seconds. How much power is produced? P = W / t = (250 joules) / 2 sec = 500 Watts

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1 Horsepower is equal to 745.56 Watts or 550 ft lb/sec

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The effort force is applied to a machine.

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The resistance force is applied by a machine.

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The number of times a machine multiplies the effort force.

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Work output Work input X 100

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Inclined Plane

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An 800 pound motorcycle is rolled up a 10 foot ramp into a pickup bed that is 3 feet off the ground. Calculate input work. Calculate output work. Calculate efficiency %.

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Work input = 10 ft X 800 lb = 8000 ft lb Work output = 3 ft X 800 lb = 2400 ft lb

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Work output Work input X 100 % Efficiency = 2400 ft lb 8000 ft lb X 100 0.3 X 100 = 30% Efficiency

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Length Height = Mechanical Advantage = 10 ft 3 ft = 3.33 mechanical advantage

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Machines make work

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easier or faster...

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but machines NEVER

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produce more work

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than is put into them.

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In fact, because of friction,

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more work goes

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into a machine

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than comes out.

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Climbing cars - 24 min

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In 1868, a motion was passed in congress to abolish the U.S. Patent Office because all important discoveries had already been made.

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Make work easier because the effort force moves over a greater distance than the resistance force.

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Inclined Plane - 2 min

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Force is multiplied since it is applied to a wide area and exerted over a small area.

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Wedge - 2 min

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Multiplies an effort force by acting through a long effort distance.

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Screw - 1 min

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A bar which moves freely around a fixed position, or fulcrum.

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Levers - 3 min

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Three Parts of a Lever Effort Force Resistance Force Fulcrum

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The Fulcrum is between the Effort Force and the Resistance force

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Multiplies Effort Force and changes its direction

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The Resistance is between the Effort Force and the Fulcrum

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Multiplies the Effort Force but does not change its direction

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The Effort Force is between the Resistance Force and the Fulcrum

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Does not multiply the Effort Force and does not change its direction.

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Does not multiply the Effort Force and does not change its direction. What DOES it do??

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Direction of the Effort Force is changed. Mechanical Advantage = 0

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Direction of the Effort Force is not changed. Mechanical Advantage = 1

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Direction of the Effort Force is changed. Mechanical Advantage is equal to the number of supporting ropes.

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Pulleys - 1 min

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A fixed pulley does not have a mechanical advantage. Fixed pulleys only change the direction of the force.

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A movable pulley has a mechanical advantage. The effort force is in the direction of the movement of the resistance.

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Two wheels of different sizes connected - the axle being the smaller wheel.

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Wheel & Axle - 1 min

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Worm Gear

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Compound Machines - 4 min

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