2 Describing MotionMotion: the state in which one object’s distance from another is changing.Are You Moving?Reference Point: place or object used for comparison to determine if something’s in motionGood Stationary RPs: Trees, Signs, BuildingsThe Backwards Moving BusAn Object Is In Motion If It Changes Position Relative To A Reference PointAre you moving? Eyes- yes Stomach- Yes…. Changing distance from chair? NO… So NOT MOVING. Except for the figgity kids
3 Relative Motion Wait… Are you sure you aren’t moving? Movement Depends on your Reference PointChair- NO SUN- YESWe are actually moving at 30 k/secAir Plane & Skydiver Demo p.8
4 System of MeasurementReally Important Experiment…. but different unitsIt’s important scientists can communicate togetherThey must have a “universal language”Metric System- International System of Units or S.IBase 10Length (meter)1 meter = 39.4 inches or .91 yardsCentimeters (cm) are used to measures distances less than 1 meter100 centimeters in 1 meter
5 Easy Conversions! Kicking (Kilo) Her (Hecto) Down (Deka) May (meter, gram, liter)Damage (Deci)Carol’s (Centi)Mind (Milli)UP to the LEFT, DOWN to the RIGHT
6 Calculating SpeedIf you know the distance an object travels in a certain amount of time, you can calculate the speedSpeed = DistanceTimeSpeed: distance object travels per unit of timeVarious ways to express speed: m/s or km/hAverage Speed: total distance & total timeInstantaneous Speed: rate at which an object is moving at a given instant timeDiscuss when average speed and instantaneous speed is beneficial: cops care about instantaneous speed!
7 Velocity & Graphing Motion A storm is coming at a speed of 25 km/h!!!Velocity: Speed AND Direction of an object’s motionWhat if you want to show somebody motion?Line Graph: plotting distance (y) vs. time (x)Slope: steepness of the lineSlope = Rise / RunRise: vertical difference between two pointsRun: horizontal difference between two pointsIt is very impressive to show your gf a graph of how fast you can run!
8 Motion of Earth’s Plates Plates: major pieces of Earth’s rocky outer layerFit together like puzzle pieces- PangaeaTheory of Plate Tectonics: Earth’s landmasses have changed position over time because they are part of plates that are moving slowlyWhy they movin’?Heat from below the Earth pushes rock upThe cooler rock gets pushed aside and sinks downSlow moving action of rock causes plate movement“Here Comes the Hot Lava”
9 Plate Movement OMG! The Plates are gonna collide! Plates move at a rate of only a few mm-cm each yearDistance = Speed X TimeDistance = 5 cm / year X 1,000 yrs = 5,000 cm
11 Acceleration The Crazy Life of a Baseball Acceleration = Speeding Up….. NOT!!!Acceleration: rate at which velocity changesIncrease speed, decrease speed, change direction- examples??Can an object at a constant speed accelerate?Yes!! changing lanes, running a curve, ferris wheelLife of a baseball- At rest, speeds up, slows down, stops, changes direction, speeds up, slows down, stops.
12 Calculating Acceleration Acceleration = Final Speed – Initial SpeedTimeUnits: meters/sec per second m/s2Let’s Practice!The Black Eyed Peas private plane is about to take off. It reaches a final speed on the runway of 40 m/s after 5 seconds. What is the acceleration of the plane?
13 Graphing Acceleration What can we tell from this graph?Increasing SpeedConstant Acceleration
14 Graphing Acceleration What can we tell from this graph?Curve= aEach second traveled a greater distance & speed than the second beforeSpeed Increasing
15 Forces Force: a push or pull described by its strength and direction Newton (N): SI Unit used for measuring the strength of a forceExert about 1 N when lifting up a lemonWe represent forces using arrowsArrows point in the direction of the forceLength of arrow tells strength- Longer = Bigger F
16 Combining ForcesNet Force: combination of all forces acting on an objectDetermines if an object movesDetermines which direction an object moves5 N5 N=10 N5 N10 N5 N=5 N5 N=
17 Unbalanced & Balanced Forces Unbalanced Force: a net force acting on an object causing it to start or stop moving or change directionCauses a change in the object’s motionBalanced Forces: equal forces acting on one object in opposite directionsCauses no change in the object’s motionUnbalancedBalanced5 N5 N5 N5 N=10 N5 N10 N10 N10 N10 N=5 N5 N5 N5 N5 N5 N5 N5 N5 N5 N5 N5 N====
18 FrictionFriction: force that 2 objects exert on each other when they rub togetherStrength of the force of friction depends on:1.) How hard the surfaces push together2.) The types of surfaces involvedLet’s try it! Rub your hands togetherFriction always acts in the opposite direction to the direction of the objects motionMetal Slides… Yikes!Without friction, moving objects might not stop until it hits another object
19 Types of Friction Static: acts on objects that aren’t moving requires extra force to start motion of objects at restMoving a Desk & Body Builders moving carsSliding: two solid surfaces slide over each otherSand on ice, chalk on hands, brakes of bike
20 Types of Friction Rolling: objects roll across a surface Easier to overcome than sliding frictionSkateboards & Bikes use ball bearingsFluid: solid objects move through a fluidUse of water, oil, or airWD40 (oil), streamlined helmet (air), hairy legs (Water) eek!
21 Gravity Gravity: force that pulls objects toward each other Issac Newton- Law of Universal GravitationGravity acts everywhere in the universe!A force acts to pull objects straight down toward the center of EarthThe Famous Apple!
22 Factors of Gravity, Weight, & Mass 2 Things Affect Gravitational AttractionMass- amount of matter in an object (gram)More mass = Great Gravitational ForceDistanceFarther apart = Less Gravitational ForceMass & Weight are NOT the SAMEWeight- measure of gravitational force exertedForce of gravity on person/object at surface of a planetWeight varies w/ strength of gravities force, mass doesn’t
23 Gravity & MotionFree Fall: motion of a falling object when the only force acting on it is gravityForce of gravity is unbalancedObjects in free fall are acceleratingAcceleration due to gravity on Earth = 9.8 m/s2All objects in free fall accelerate at the same rate regardless of massDemonstrate Free Fall with various objects…. Get students helping. When two objects don’t fall at same rate, “might as well go home!”Flat Paper vs. Crumbled PaperPlay Song Free Falling!
24 Gravity & MotionAir Resistance: fluid friction experienced by objects falling through the airUpward force exerted on all falling objects in airObjects with more surface area = more resistanceAir resistance increases with velocityAs object speeds up, resistance gets greater & greaterEventually force of air resistance & gravity are equalForce is balanced, no acceleration, constant velocityTerminal Velocity: greatest velocity a falling object reaches when force of air resistance equals weight of objectAn object that is thrown vertically will land at the same time as an object that was dropped
25 First Law of Motion- Inertia An object at rest will remain at rest, and an object moving at a constant velocity will remain moving at a constant velocity unless it is acted upon by an unbalanced (net) forceTennis Game- Ball moves until gravity or friction change objects motionIf an object is not moving, it will not move until a force acts on itClothes on your bedroom floor!Get a student volunteer and flick a card with pennies off their head
26 Inertia Inertia: tendency of object to resist change in motion Greater the mass of object = Greater Inertia =Greater force needed to change its motion
31 Second Law of MotionAcceleration depends on the object’s mass and on the force acting on the objectForce = Mass X Acceleration F = M x AUnit of Force = Newtons (N)Increase Acceleration = Increase ForceIncrease Mass = Decrease AccelerationBoo Yah! Practice Problem!You are cruzin’ the streets of Mattoon with an acceleration of 20 m/s in your Lamborghini that has a mass of 1250 kg. What is the net force?20 m/s = 45 mph
32 Third Law of MotionIf one object exerts a force on another object, then the second object exerts a force of equal strength in the opposite direction of the first object…. What????For every action there is an equal but opposite reactionAction Reaction Pairs: Examples…?Balloon Trick
33 Action Reaction Forces Cancel? “Ms. Genta, you said before, forces with equal and opposite direction cancel out and cause no movement…??? You must be trippin!”Don’t Cancel If Acting on DIFFERENT objects!Ball downward force on wrists, Wrists upward force on ballAll players exerting a force on the ball
34 Momentum Momentum: quantity of motion Momentum = Mass x Velocity (kg m/s)Momentum of an object is in the same direction as its velocityMore Momentum = Harder to StopWhat same velocity, different mass?Car & Baseball both moving at 20 m/sLaw of Conservation of Momentum: in the absence of outside forces, it can be transferred from one object to another, but none is lost
36 Rocket MotionRockets rise into the air because it expels gases with a downward force, then the gases exert an equal but opposite reaction force on the rocketUpward thrust is greater than downward gravityCentripetal force: causes an object to move in a circleForce on satellites that are accelerating & revolving around EarthSatellites in orbit around Earth continuously fall towards Earth, but because Earth is curved they travel around it
37 What is Work?Work: force exerted on an object causing it to move in the same direction as the forcePushing a swing, lifting bags up, pulling blinds downIt is not work unless the object moves!Pushing a car, lifting an enormous boulderIt is not work unless the motion is in the same direction as the forceCarrying your books to classThe good news: Homework is not work!!
38 Calculating WorkThe amount of work you do depends on both the amount of force you exert and the distance the object movesWork = force X distanceMeasured in Joules (J)Work done to exert a force of 1 Newton/ 1 MeterHeavier Object = Greater WorkGreater Distance = Greater WorkLet’s Practice!An old, precious lady asks you to move her 95 N sewing kit a distance of 12 m. How much work are you going to have to exert?
39 PowerIf 1 person sprints up the stairs with a box and 1 person creeps up the stairs with the same box, you are doing the same amount of work but….Power: the amount of work done on an object in a unit of timePower = Work or Power = Force X DistanceTime TimeUnit of Power: Watts (W) = 1 J/sSo… more power to sprint up the stairs!Mr. Smith exerts a force of 900 N to push a cart of ice cream down to Ms. Genta’s amazing science students! Oh Ya! The cart moves 250 meters in 40 seconds. What is the power of Mr. Smith?
40 What is a Machine? Machine: device that allows work to be easier Hands, shovel, wheelbarrow, craneMachines make work easier by changing either the force, distance, or directionInput Force: force exerted on the machineInput force moves machine- input distanceOutput Force: force machine exerts on objectMachine exerts a force- output distanceInput Work = Input Force X Input DistanceOutput work is never greater than Input work
41 Mechanical Advantage Mechanical Advantage = Output Force Input Force Mechanical Advantage the number of times a machines increases a force exerted on itIncrease Force: M.A greater than 1You input 10 N on a can openerCan opener outputs 30 N on the canMechanical advantage of 3Increase Distance : M.A less than 1You input 20 N on a stress ballStress ball outputs 10 N on your handMechanical advantage of 0.5Changing Direction: M.A always equal to 1Input force is the same as output force
42 Efficiency of Machines Efficiency: compares output & inputEfficiency = Output WorkInput WorkFriction decreases the efficiency of machinesThink about old rusty scissors!Efficiency of machines, always less than 100%Practice Time!Your sweet dad asks you to mow the lawn and pulls the worst lookin’ mower out the garage. I mean this thing was made in Your input is 250,000 J and the work done by the mower is 100,000 J. How efficient is this machine?X 100%
44 Simple Machines: Inclined Plane A flat, sloped surface… aka rampExert input force over a longer distanceInput force- pushing or pulling objectOutput force- lifting object without inclined planeInput far less than outputIdeal Mechanical Advantage = Length of inclineHeight of incline
45 Simple Machines: Wedge Thick at one end, gradually goes to a thin edgeLiterally moving the inclined planeIdeal Mechanical Advantage = Length of wedgeWidth of wedgeLonger, thinner the wedge, greater M.AInput Force splits into two output forcesExamples: knife, zipper, axe, sharpener, mouth
46 Simple Machines: Screws Inclined plane wrapped around cylinder -“spiral”Threads on a screw act like an incline plane to increase distance over which force is exertedScrew exerts an outward force on the woodCloser the threads, greater M.ACalculating M.A = Length around threadsLength around screwExamples: screws, jar lids, light bulb
47 Simple Machines: Levers Bar that is free to pivot or rotateon a fixed pointFixed point that a lever pivots around: FulcrumThree Classes of Levers:1.) 1st Class- always change direction of input forceScissors, pliers, seesaws, paint can opener, lifting neck2.) 2nd Class- increase force, no change directionWheelbarrow, doors, nutcrackers, bottle openers, walking3.) 3rd Class- increase distance, no change forcehockey stick, fishing pole, shovel, baseball bat, flexing
48 Simple Machines: Wheel & Axle Two circular objects fastened togetherthat rotate around a common axisObject with larger radius – WheelObject with smaller radius - AxleGreater the ratio between the radius of the wheel and the radius of the axel- Greater M.AMechanical Advantage = Radius of WheelRadius of AxelExamples: screwdriver, doorknob, fairy boat
49 Simple Machines: Pulleys Grooved wheel with a rope or cable wrapped around itFixed Pulley: attached to a structureTop of flagpoleMoveable Pulley: attached to moving objectConstruction CranesBlock & Tackle: combination of fixed & moveableMechanical advantage is equal to the number of sections of rope that supports the object
50 Compound Machines Compound machines: use two or more simple machines Handle- Wheel & AxelScrew- also part of axelWedge- Peels SkinLever- suction cup
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