Presentation on theme: "Electricity and Magnetism"— Presentation transcript:
1 Electricity and Magnetism PHYSICSUnits:Analyzing MotionWork and EnergyWavesElectricity and Magnetism
2 TN Standards - MotionCLE : Investigate the relationships among speed, position, time, velocity, and accelerationCLE.3202.Inq.2: Design and conduct scientific investigations to explore new phenomena, verify, previous results, test how well a theory predicts, and compare opposing theoriesCLE.3202.Inq.4: Apply qualitative and quantitative measures to analyze data and draw conclusions that are free of biasCLE.3202.Inq.6: Communicate and defend scientific findings
3 Chapter 11 - Motion Sections: 1 - Measuring Motion 2 - Acceleration 3 - Motion and Force
4 1 - Measuring Motion Key Questions: How is a frame of reference used to describe motion?What is the difference between speed and velocity?What do you need to know to find the speed of an object?How can you study speed by using graphs?
5 Frame of ReferenceObserve an object in relation to other objects that stay in place, called reference points.A frame of reference is used to describe the motion of an object relative to these reference points.The trees in the backgroundin Figure 1
6 Distance Distance measures the path taken To measure distance, you measure the length of the path that the object took.Displacement measures only the difference between the final and starting positions
7 Speed & Velocity Speed – how fast an object moved Velocity – gives us both speed and directionVelocity is described relative to a reference pointUp and right are positive; left and down are negative ( Cartesian Coordinate system )+y-x+x-y
8 MotionWhen an object changes position with respect to a frame of reference, the object is in motionVelocity / Speed: Distance travelled in a certain time periodDV/St
9 D V/S t Calculating Speed Need two quantities – distance travelled & timeAverage speed – distance divided by time intervalInstantaneous speedspeed at a given timevery small time intervalSpeedometer in carDV/St
10 Demonstration Slope of a distance vs. time graph equals speed Run a 6 m length ( in class? )Have your partner time youWhat is your speed?
11 Graphing MotionSometimes easier to analyze motion on graphs
12 2 - Acceleration Key Questions: What changes when an object accelerates?How do you calculate the acceleration of an object moving in a straight line?How can a graph be used to find acceleration?
13 Velocity Changes upon Acceleration Speed can change, but so can directionNotice speed is changing with each second
14 Changes in DirectionUniform circular motion has centripetal accelerationSources: friction, tensionDemonstration
15 Circular Motion Demonstration Foam ball with string attached to itSwing ball with handDiagram features of motionWhat happens when I let go of the string?
16 2 - Acceleration Key Questions: What changes when an object accelerates?How do you calculate the acceleration of an object moving in a straight line?How can a graph be used to find acceleration?
20 Calculating Acceleration Acceleration is the rate at which velocity changesAcceleration is negative when slowing down
21 Graphing Accelerated Motion The slope of a straight line on a speed vs. time graph is equal to the acceleration.Constant AccelerationCan also be seen from a distance vs. time graph
22 BELLWORKHow do we calculate average acceleration?
23 3 - Motion and Forces Key Questions: What do scientists identify as the fundamental forces of nature?What happens when there is a net force acting on an object?What force always opposes motion?Why is friction sometimes necessary?
24 Fundamental ForcesA Force is defined as any action that can change the state of motion of an objectGravity, electromagnetic force, strong nuclear force, and the weak nuclear forceFundamental forces vary in strengthForces can act through contact or at a distance
25 Balanced and Unbalanced Forces Whenever there is a net force acting on an object, the object accelerates in direction of the net forceBalanced forces do not change motionUnbalanced forces do not cancel each other
26 Friction Is a force Always opposes motion Static friction – occurs between stationary surfacesKinetic friction – occurs between moving surfacesSliding friction ( usually greater than rolling fiction )Rolling friction
27 Friction and MotionFriction is necessary for many everyday tasks to function properlyNon-stick skilletsCars would not move without friction!!Can increase helpful friction or decrease unwanted frictionSand on roads make them less slipperyLubrication reduces friction
28 Friction and Balance of Forces Cars do not or do move based on frictionConstant speedAccelerationNo Slipping
29 Demonstration – Spring Scale Drag wood and measure the force needed to overcome frictionFriction depends on force applied between surfacesRock keeps paper from being blown away by windMore weight on block more frictionRougher surface more friction