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.

What is motion?

Motion is a change in position, measured by distance and time

Motion - 12 min

A reference point is needed to measure movement

Are you moving right now?

What is your reference point?

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

Frames of Reference

Frames of Reference

Two Dimensional World

Speed is the distance traveled by a moving object over a period of time

Speed - 4 min

distance Speed = time

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

object is not always constant The speed of a moving object is not always constant

total distance Average speed = total time

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

Speed Calcaulation Practice

Graphing Speed Distance (meters) Time (seconds)

Velocity is speed in a given direction

Velocity 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?

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

Vector Addition Direction is indicated by compass degrees

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

Vector Addition

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

90o 180o 0o 270o

90o 180o 0o 270o

90o 180o 0o 270o

90o 180o 0o 270o

90o 180o 0o 270o

Practice Vector Addition

Acceleration

Acceleration is the rate of change of velocity

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

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

There is no such thing as Deceleration

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? Velocity(final) - Velocity(original) Acceleration = time 0 mph - 60 mph = 6 seconds - 60 mph = 6 seconds = - 10 miles per hour per second

Acceleration Calcaulation Practice

Centripetal Acceleration Acceleration toward the center of a circular path.

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

Centripetal Acceleration

Force provided by engine Acceleration provided by tires

Centripetal Acceleration What happens if the accelerating force is removed?

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

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

Forces cause changes in motion

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.

Force Any Push Or Pull

Forces & motion - 6 min

Balanced Forces Produce NO Motion

Unbalanced Forces Produce Motion

A force that opposes motion Friction A force that opposes motion

Types of Friction 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

Newton’s Laws - 5 min

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

Second Law of Motion F = Ma Force = mass X acceleration

For every action, there is an equal and opposite reaction. Third Law of Motion For every action, there is an equal and opposite reaction.

Rockets - 6 min

Momentum mass X velocity

Momentum mass X velocity

Momentum - 8 min

Does a long pendulum swing faster than a short one?

Does a heavy pendulum swing faster than a light one?

Momentum is the same before and after a collision

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

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

Collisions M1V1 = M2V2 Before After

Colliding objects have same mass Elastic Collision

Heavy object strikes light object Elastic Collision

Light object strikes heavy object Elastic Collision

Colliding objects have same mass Inelastic Collision

Rollercoasters work because of momentum

Rollercoaster Physics

Rollercoasters - 24 min

Is work being done?

Units of Force are Newtons Units of Distance are Meters Work = F d Units of Force are Newtons Units of Distance are Meters Newton Meters = Joules

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

Work & Power - 15 min

power - 2 min

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

Work & Power Calcaulation Practice

Bus

Machines make work easier

Machines make work easier by changing the size or direction of a force

Climbing cars - 24 min

2 forces are related to machines

The effort force is applied to a machine. 2 forces are related to machines The effort force is applied to a machine.

The resistance force is applied by a machine. 2 forces are related to machines The resistance force is applied by a machine.

The number of times a machine multiplies the effort force. Mechanical Advantage The number of times a machine multiplies the effort force.

Work output Work input X 100 Efficiency % Work output Work input X 100

Inventors

Da Vinci - 8 min

Simple Machines

Do work with one motion Simple Machines

6 Simple MachineS Inclined Plane Lever Pulley Wedge Screw Wheel & Axle

Work is made easier because the effort force moves over a greater distance.

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 can move freely around a fixed position, or fulcrum.

Levers - 3 min

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

Types of Pulleys Fixed Movable

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

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

Direction of the Effort Force is changed. Pulley System 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 does have 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

Simple Machine Combinations

Compound Machines - 4 min

Rube Goldberg Device

Rube Goldberg Device

Rube Goldberg Device

Rube Goldberg Device

Rube Goldberg Device

END Content Standard 2.1