# Position and Motion.

## Presentation on theme: "Position and Motion."— Presentation transcript:

Position and Motion

What is motion? An object is in motion if its position changes relative to a reference point Reference point: place or object used for comparison to determine if something is in motion

Motion is Relative Motion is relative – it depends on where the reference point is You may not be moving according to one reference point, but you may be moving according to another. Carousel – page 6

Practice Problems Jane is sitting in the family car. Her mother is driving her from their house to the library. Jane waves as she passes her friend Marina. Which of the following is not moving with respect to Jane? Marina The family car The library Jane’s house

Practice Problems What is the best reference point for describing the motion of planets around the solar system? What is the best reference point for describing the motion of the moon around the Earth?

Exploring Reference Points
The reference point determines if the object seems to be still or be in motion. Ex: a crow is flying along carrying a ball. Suddenly, the crow accidentally drops the ball and watches it fall. A person is standing on the ground watching the crow and the ball.

Exploring Reference Points
If the crow is the reference point, in what direction is the ball falling? If the woman is the reference point, in what direction is the ball falling?

You are standing at your locker and your friend is walking towards. The next day, you see your friend walking towards you and you decide to start walking towards him too. To you, (as the reference point) does he seem to moving slower or faster than yesterday?

You are standing outside of school on the turnpike waiting for your ride home. The speed limit on the turnpike is 35 mi/hr. How fast are the cars moving passed you? Now you are in the car driving down the road (at the speed limit, of course) and you are passing cars along the way. How fast is YOUR car moving in relation to you? How fast are the other cars moving passed you?

Which objects are in motion?
Two trucks are heading towards each other, and there is a person standing still in between. Truck #1 is travelling at 30 mi/hr in the direction shown. Truck #2 is travelling at 20 mi/hr in the direction shown. According to the person, how fast are trucks 1 and 2 moving? According to truck 1, how fast is the person and truck 2 moving? According to truck 2, how fast is the person and truck 1 moving?

Enriched Problem – try with a partner
CC Sabathia throws a 90 mi/hr fast ball. CC is standing at the back of the Yankees bus that is traveling 60 mi/hr down the highway (going to beat the Red Sox). CC decides to begin warming up and throws a pitch from the back to the front of the bus. Brett Gardner, another Yankee, sees CC’s pitch as being how fast? If a fan standing on the side of the road saw CC’s pitch, how fast would they see it?

Distance, Speed, and Time

What is speed? The speed of an object is the distance the object moves per unit of time (it is a type of rate)

How to calculate speed Speed is equal to the distance the object travels, divided by the amount of time it takes to travel that distance. Speed = distance ÷ time

Steps to solve speed problems
Read the entire problem Write down what you are given (speed, distance, time) Write down what you need to find out (speed, distance, time) Draw the triangle Cover the part of the triangle that you are looking for Divide or multiply to solve the problem Write your answer with the correct units!

Understanding the meaning of rates
If a car is driving 10 miles per hour, how far has the car gone in one hour? If an airplane flies at 260 meters per second, how far has the plane gone in one second?

Speed problems A swimmer swam 6 km in 0.2 hours. What was the swimmer’s speed? A runner ran a 26 mile marathon in 5 hours. What was the runner’s speed? A police car chased a truck for 30 miles and it took 20 minutes. How fast was the police officer going?

A bit more difficult… Odell Beckham Jr. runs at a speed of 7 km/hr. How long would it take him to run 400 kilometers assuming he does not get tired and slow down. McKayla Maroney (Olympic gymnast) runs 60 ft. at a speed of 15 ft/sec. How long does it take her to get to the vault?

Even more difficult… A train leaves NYC and begins traveling 3,000 miles to L.A. The train drives at a constant speed of 80 mi/hr without stopping along the way. If the train leaves at 1 a.m. (eastern time), what time will is arrive in L.A. (eastern time)? After arriving in L.A., the train drops off passengers and begins traveling to Austin Texas. The train keeps the same speed (80mi/hr) and travels for 17.5 hours until it reaches its destination. How far is Austin from L.A.?

Velocity

What is velocity? The velocity of an object is the objects speed in a given direction. Ex: Speed The car is moving at 40 miles/hour The girl is running at a speed of 5 km/hour Velocity The car is moving north at a speed of 40 miles/hour The storm is moving 25km/hr eastward

How to calculate velocity
Velocity is equal to the distance the object travels, divided by the amount of time it takes to travel that distance in a certain direction Velocity = distance ÷ time (in a certain direction) Solve same way you would solve speed problems (using velocity = to speed) and including direction in your answer!

Practice Problems A flock of birds are flying 300 miles south for winter. It takes them 12.5 hours to reach their winter home. What is the speed of the flock of birds? What is the velocity of the flock or birds?

Try to solve these with a partner
Amber walked to talk to her friend Maria on her way to the pool. Amber walked 400 meters westward for four minutes until she met up with Maria. After talking with Maria for 3 minutes, Amber continued walking another 400 meters westward towards the pool for six more minutes. Identify all of the following: How far did Amber travel in total? How long did it take Amber to get to the pool? What was Amber’s velocity during each portion of the trip?

Let’s think back to this problem
CC Sabathia throws a 90 mi/hr fast ball. CC is standing at the back of the Yankees bus that is traveling north 60 mi/hr down the highway (going to beat the Red Sox). CC decides to begin warming up and throws a pitch from the back to the front of the bus. A fan standing on the side of the road saw CC’s pitch and clocked it as how fast? What was the velocity of his pitch?

Let’s go a bit more in depth…
The fan clocked CC’s pitch as traveling 150 mi/hr. Now, CC decided to stand in the front of the bus and throw towards the back so he would not distract the driver. The bus is till traveling north at 60 mi/hr and CC’s arm has yet to get tired (still throwing 90 mi/hr). Now what speed would the fan on the side of the road see? What would the velocity be?

More practice Car A travels EAST at an average speed of 20 miles per hour for 3 hours and then stops. Car B travels WEST at an average speed of 50 miles per hour for 2 hours and then stops. Both cars start from the same place. How far apart are the cars? Two tigers are hunting deer. The tigers start from the same place, but run in OPPOSITE directions to catch their own deer. Tiger #1 runs at an average speed of 30 miles per hour for 1 hour to track down his deer. Tiger #2 runs at an average speed of 20 miles per hour for 1 hour to catch its deer. How far apart are the tigers eating?

Now try creating your own problems!

Acceleration

What is acceleration? Acceleration – the rate at which velocity changes Refers to an increase in speed, a decrease in speed (deceleration), or a change in direction Note: a change in direction = a change in velocity

Calculating acceleration
Acceleration is the change in speed per unit of time. Acceleration = (final speed – initial speed) ÷ time Acceleration = (24m/s – 0m/s) ÷ (3 sec) Acceleration of the plane = 8 m/s^2

Practice A racecar travels at 20 feet per second while they clear the track of an accident. When the race resumes, the car speeds up to 100 feet per second in exactly 5 seconds. What is the acceleration of the car?

A car advertisement says its car can go from a speed of zero to 80 miles per hour in a time of .001 hr! What is the acceleration of that car? Rock’N’ Rollercoaster in Disney World claims to go from 0 to mi/s in 2.8 seconds. What is the acceleration of the rollercoaster?

Trip to the Cayman Islands
You are taking a trip to the Cayman Islands. The airplane starts from rest (0 m/s) and speeds up to 65 m/s in 8 seconds. What is the plane’s acceleration? After a long flight, you are about to land on Grand Cayman! The plane is traveling at a speed of 72 m/s and safely lands and stops in 8.6 seconds. What is the deceleration of the plane?

Trip to the Cayman Islands
While on Grand Cayman, you and your family decide to go to an amusement park! You go on a rollercoaster that twists, turns, and flips. The rollercoaster increases to .016 mi/s in just 3 seconds. What is the acceleration of the rollercoaster? The rollercoaster stays at .016 mi/s throughout the entire ride until it is over. It takes 5.2 seconds to come to a complete stop. What is the deceleration of the rollercoaster?

This may be tricky… Your rollercoaster accelerates to 57 mi/hr (at the beginning of the ride) and then continues at a constant speed. Does it accelerate in any way prior to the ride ending? Why or why not?

Forces

What is a force? Force: a push or pull on an object
Includes strength and direction (like velocity) The SI unit used to measure force = newton (N)

Net Forces Net Force: combination of all forces acting on an object
Determines if and how an object will accelerate

Balanced and Unbalanced Forces
Will NOT cause change in an object’s motion Forces “cancel” each other out Net force = 0 Will cause change in an object’s motion Forces DO NOT “cancel” out Net force ≠ 0

Free Body Diagrams (FBD)
Draw a box to for the object Add arrows (for direction) with strength of all forces acting on object

Let’s Try This Together
Two dogs are pushing against their box of food. Using the picture to the right, draw a free body diagram. Then, determine the net force acting on the box of food.

Try these with a partner
Mrs. K’s car got stuck in the snow last week. When trying to get it out, she exerted a 23 N force on her car towards the left but it wouldn’t budge. Her husband started to help her and exerted an additional 27 N force towards the left on her car. Draw a FBD and determine the force it took the move Mrs. K’s car out from the snow. Mrs. Kopacz pulls on her dog’s leash to the right with an 18 N force. Her dog pulls to the left with a 8 N force. Draw a FBD and then determine the net force on the leash.

Individual practice Mrs. Kopacz and Miss Aquino were playing tug o’ war over the weekend. Mrs. K pulled to the left with a 20 N force. Mrs. Aquino pulled to the right with a 23 N force. Draw a FBD and determine the net force acting on the rope. Who won tug o’ war? How do you know?

Inertia

What is Inertia? Inertia – resistance to change in motion
Inertia depends on mass: more mass = more inertia = more force needed to move it

Examples of Inertia

Newton’s Laws of Motion

Newton’s First Law of Motion
Law of Inertia An object at rest will remain at rest unless acted upon by an outside force An object in motion will stay in motion unless acted upon by an outside force

Newton’s Second Law of Motion
An object’s acceleration depends on its mass and the net force acting on it Force = mass x acceleration

Calculating Force F = ma You can use the triangle! A 10 kg box accelerated up the hill at 2 m/s². What force is exerted on the box? A 15 kg box is slid across the floor with an acceleration of 3m/s². What force is needed for this motion?

Try to create your own force word problems!
Then, trade with a partner and solve.

Newton’s Third Law of Motion
If one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction on the first object. Many sports (including gymnastics) exemplify this law

Newton’s 3rd Law of Motion
While driving down the road, a firefly strikes the windshield of a bus and makes a quite obvious mess in front of the face of the driver. This is a clear case of Newton's third law of motion. The firefly hit the bus and the bus hits the firefly. Which of the two forces is greater: the force on the firefly or the force on the bus?

Energy

Energy: The ability to do work or cause change
What is energy? Energy: The ability to do work or cause change Units = Joules ( J) Energy Video

Two Main Types of Energy
Potential Kinetic Energy an object has due to its position Gravitational and elastic Energy an object has due to its motion Depends on speed and mass of object

What is Mechanical Energy?
Mechanical Energy – combination of kinetic and potential energy

Law of Conservation of Energy
Energy cannot be created or destroyed Energy is transformed (changed) into another form of energy – no energy is lost in a process

Law of Conservation of Energy
Look at the rollercoaster on pgs 124 and 125 in your textbooks. With your shoulder partner, answer numbers 1, 2, and 3. I wish we could do this in class!

Who caught on? Since we have been talking about energy and the law of conservation, who caught on to why / how rollercoasters stop? Let’s watch this again and see if we notice.

Waves and light Sections 1.1 and 1.2

WAVES Wave: a disturbance that transfers energy from place to place
Most waves need to travel through a medium Medium: material through which a wave travels through (ex. water, air)

Types of Waves Transverse Longitudinal

Transverse waves: medium particles move across (up & down) the direction of the wave
Crest: high point of wave Trough: low point of wave A water wave is an example of a transverse wave. As water particles move up and down, the water wave itself appears to move to the right or left

2. Longitudinal waves: medium particles move back and forth in the same direction in which the wave travels -Coils move forward and then back Energy travels from one end of the spring to the other creating a wave -After the wave passes, each coil returns to the position where it started

Comparison of Waves We will mainly discuss transverse waves

Properties of transverse Waves
- Crest = Top of the wave - Trough = Bottom of the wave - Wavelength = The length of a complete wave from crest-to-crest or trough-to-trough - Amplitude = Height of the wave from equilibrium

Why does this matter? A smaller wavelength = higher energy
Frequency: amount of waves per second Waves on the electromagnetic spectrum all have DIFFERENT FREQUENCIES

Electromagnetic spectrum
Section 3.2

Rattlesnakes May Inject Venum Under eXtreme aGitation

How can we tell them apart?
DIFFERENT FREQUENCIES We can only see VISIBLE LIGHT

Visible light Section 4.1

Visible light

Wavelength and frequency of each color

Vocabulary to know Transparent: material that allows most or ALL light to pass through (clear) Translucent: material that allows SOME light to pass through (clear colored) Opaque: material that does NOT allow ANY light to pass through (all light is reflected or absorbed)

Colored light

rainbows White light is not a single color; it is made up of a mixture of the seven colors of the rainbow. We can demonstrate this by splitting white light with a prism: How do you think rainbows are formed?

Reflection and refraction
Sections 4.2 and 4.3

How we see colors The colors that we see are REFLECTED off of the object – all other colors are ABSORBED Ex: a shirt appears light blue (reflects blue) The shirt absorbs other colors EX: a shirt appears white (reflects white)

reflection Reflection occurs when light bounces off a surface
Light rays reflected in a mirror cause an inverted image

refraction Refraction occurs when light BENDS as it crosses through material

What does refraction looks like

Lenses and mirrors Sections 4.2 – 4.4

View kacleaveland's map
Taken in a place with no name (See more photos or videos here) View kacleaveland's map "Have you ever approached a giant concave mirror? See your upside-down image suspended in mid-air. Walk through the image to see a new reflection, right-side-up and greatly magnified. In the background you see reflected a room full of visitors enjoying other Concave Mirrors Curves inward Images look bigger

Convex Mirrors Curves outward Images look smaller
Use: Rear view mirrors, store security… CAUTION! Objects are closer than they appear!

Concave Lenses Lenses that are thicker at the edges and thinner in the center. Images look smaller

Convex Lenses Thicker in the center than edges. Images look bigger

The Human Eye The human eye is a complex structure with many parts that allow you to see. Use the words in the word bank to identify the parts of the eye.

Electricity and Electromagnetism

Review of Charge Protons = Positive Charge Electrons = Negative Charge
Opposites Attract Like Charges Repel

What is electricity? Electricity is the flow of electrical power or charge. Electricity is a form of energy. Electricity is the flow of electrons.

Static Electricity Transfer of charge from one object to another
Rubbing your feet against the carpet Rubbing a balloon against a sweater

Lightning – Ultimate Static Discharge
Thunderstorms have violent air currents Water drops rub up against ice crystals One area of the cloud becomes negative One area of the cloud becomes positive Result: STATIC DISCHARGE If the bottom of the cloud gets enough of a negative charge, discharge can go from cloud to ground

How does electricity get to your home?
Electromagnetism How does electricity get to your home?

Electromagnet Electricity in a wire produces a magnetic field
If a piece of iron is wrapped around the wire, the iron becomes a temporary magnet Disconnect the power The magnetic field stops The iron loses magnetism quickly

AC/DC Electricity from generators are “Alternating Current”
It flows in two directions over and over again Power in your house is alternating current You can change ‘AC’ into ‘DC’ Battery power is “Direct Current” It flows in one direction From one side of the battery to the other

Transformers (NOT Robots in Disguise)
When electricity leaves a generator, it needs a huge push to get to your house (Hundreds of miles away) Step-Up Transformer The voltage is high, but it can only push so hard. The force needs to be increased if it is going to get from Niagara Falls to you.

Step-Down Transformer
The electricity gets to the sub- station near your home. It doesn’t need a big push anymore because it has a shorter distance to go Too much push from such a short distance could be too much for your house to handle (120 volts) Step-Down Transformer

Electrical Circuits In order for electricity to go from one place to another, you need a “circuit” Electrical Circuit – A complete, unbroken path that electricity can flow from one place to another

Conductors – A material through which electric current can pass easily Examples: Any metal (especially copper) Water Insulators – A material through which electricity cannot pass Used to cover wires so they can be handled Rubber Plastic

Circuit Terminology Current = The amount of electrons flowing in a wire Voltage = The force that pushes electrons through a wire The stronger the force, the more current gets pushed through the wire Resistance = The force that reduces current in a wire. The stronger the resistance, the smaller the amount of current

Circuit Terminology Current = amperes (amps) (A) Voltage = volts (V)
Resistance = Ohms (Ω)

Batteries Provide Voltage Filled with electrons
Electrons are attracted to the positive terminal

Ohm’s Law Current = Voltage divided by Resistance

Practice Problems What is the current in a 1.5 Volt circuit that has a resistance of 3 Ohms? There is a current of .25 Amps in a circuit that has a voltage of 4.5 Volts. What is the resistance in this circuit? A circuit has a resistance of 6 Ohms and .5 Amps of current. What is the voltage of this circuit?

Series Circuit There is only ONE path for the electrons to get to the positive terminal

Parallel Circuit More than one way to get to the positive terminal

Calculate Power Power: rate at which energy transforms from one form to another Power = voltage x current Power (kW) Voltage (V) Current (Amps)

Paying for Electricity
You pay for energy used, not power! Energy = power x time Energy (kWh) Power (kW) Time (h) When figuring out payments for electricity, find power, and then find energy used.