 # 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.

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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.

Motion - 12 min

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

The whole galaxy rotates at 490,000 mph

Two Dimensional World

Speed= distance time

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

Average speed= total distance total time

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

Distance (meters) Time (seconds)

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

Vectors - 12 min

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

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

Direction is indicated by compass degrees

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

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?

0o0o 90 o 180 o 270 o

0o0o 90 o 180 o 270 o

0o0o 90 o 180 o 270 o

0o0o 90 o 180 o 270 o

0o0o 90 o 180 o 270 o

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?

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

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?

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

Acceleration toward the center of a circular path.

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

Force provided by engine Acceleration provided by tires

What happens if the accelerating force is removed?

The object moves in a straight line.

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

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

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

What's actually happening?

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.

Produce NO Motion

Produce Motion

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

Newton’s Laws - 5 min

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

Force = mass X acceleration F = Ma

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

Rockets - 6 min

Momentum - 8 min

Does a long pendulum swing faster than a short one?

Does a heavy pendulum swing faster than a light one?

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

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

M 1 V 1 = M 2 V 2 Before After

Colliding objects have same mass Elastic Collision

Heavy object strikes light object Elastic Collision

Light object strikes heavy object Elastic Collision

Inelastic Collision Colliding objects have same mass

Rollercoasters - 4 min

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

Work - 2 min

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

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

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

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

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

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

power - 2 min

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

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

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

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

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

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

The effort force is applied to a machine.

The resistance force is applied by a machine.

The number of times a machine multiplies the effort force.

Work output Work input X 100

Inclined Plane

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 %.

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

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

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

Machines make work

easier or faster...

but machines NEVER

produce more work

than is put into them.

In fact, because of friction,

more work goes

into a machine

than comes out.

Climbing cars - 24 min

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

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

Inclined Plane - 2 min

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

Wedge - 2 min

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

Screw - 1 min

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

Levers - 3 min

Three Parts of a Lever Effort Force Resistance Force Fulcrum

The Fulcrum is between the Effort Force and the Resistance force

Multiplies Effort Force and changes its direction

The Resistance is between the Effort Force and the Fulcrum

Multiplies the Effort Force but does not change its direction

The Effort Force is between the Resistance Force and the Fulcrum

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

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

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

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

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

Pulleys - 1 min

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

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

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

Wheel & Axle - 1 min

Worm Gear

Compound Machines - 4 min

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