2 Physics Comp Book UNIT 1: Linear Motion (@top, BIG!) p. 1 Copy GPS listed on the LTA. Circle the verbs; underline the nouns.Page Contents2 Concept Map: Linear Motion pt. 13 linear motion, distance4 displacement, speed5 velocity, acceleration6 Venn Diagram: Scalar vs. Vector7 Concept Map: Linear Motion pt. 28 Lab SUMUPS:* Distance vs. Displacement* Froggy
3 Let’s do a Frayer model for linear motion: Definition:Drawing:Motion in a straight linelinear motionverticalhorizontalWhat it’s NOT:How to remember:
4 Concept Map: Linear Motion p. 2 when an object moves we observe— which is calculated bycalledThe position changingHow quickly the position changesThe rate at which the movement changes
5 When an object moves, we can observe: For your concept map on p.2 of comp book!The position changingDistance: how far it travels is called (in meters)Displacement: how far its position is from the starting point (in meters with a direction)How quickly the position changesSpeed: how fast it’s covering distance(or how much distance is covered in an amount of time)Velocity: how fast it’s position is moving and in what direction relative to some other point (like home or a destinationThe rate at which the movement changesAcceleration: is it speeding up or slowing down
6 Displacement Isn’t Distance The displacement of an object is not the same as the distance it travelsExample: Throw a ball straight up and then catch it at the same point you released itThe distance is twice the heightThe displacement is zero
8 Distance & Displacement B4 m5 m3 mYou walk from A to B to C.What is your distance traveled?What is your displacement from A?AYour distance traveled is 7mYour displacement form A is 5 m
9 Let’s do Frayers for distance & displacement in your comp book: How to calculate:Definition:How to remember:Don’t confuse this with:
10 Types of SpeedInstantaneous Speed is the speed at any specific instance or moment in timeEx. On a speedometer reading…you are traveling 35 mph (mi/hr)or 50 km/h or 25 m/sAverage Speed is the total distance covered divided by total time
11 How do you calculate average speed? The average speed of an object is defined as the total distance traveled divided by the total time elapsedOR take the average:(initial speed + final speed)2Speed is a scalar quantity… why is it not a vector?
12 Speed, contAverage speed totally ignores any variations in the object’s actual motion during the tripThe total distance and the total time are all that is importantSI units are m/s
13 Speed & Velocity Speed is the distance traveled in a certain time. Velocity is the displacement traveled in a certain time.Velocity is speed in a given direction.
14 VelocityThe average velocity of an object is defined as the total displacement traveled divided by the total time elapsedVelocity is a vector quantity
15 Velocity It takes time for an object to undergo a displacement The average velocity is rate at which the displacement occursgenerally use a time interval, so let ti = 0
16 Velocity, cont.Direction will be the same as the direction of the displacement (time interval is always positive)+ or - is sufficient to indicate directionUnits of velocity are m/s (SI), cm/s (cgs) or ft/s (US Cust.)Other units may be given in a problem, but generally will need to be converted to these
17 Speed vs. VelocityCars on both paths have the same average velocity since they had the same displacement in the same time intervalThe car on the blue path will have a greater average speed since the distance it traveled is larger
18 Let’s do Frayers for speed & velocity in your comp book: How to calculate:Definition:Wait for the next slideHow to remember:Don’t confuse this with:
19 Speed vs. Velocity You drive from Yakima to Seattle (140 miles away) You stop in Ellensburg for a 2 hr lunch with a friend.Your total driving time is 2 hoursWhat is the average speed?What is the average velocity?(solve these questions in the Frayers)LIST (3) Equation(2) LABEL w/units (4) Solve
20 Constant Velocity Constant velocity is constant velocity The instantaneous velocities are always the sameAll the instantaneous velocities will also equal the average velocity
22 How fast is the plane moving in respect to the ground? Velocity Example 2How fast is the plane moving in respect to the ground?
23 Velocity Example 2How fast is the plane moving in respect to the ground? Notice the two velocities are occuring in the same LINE (linear motion…)
24 Velocity Example 3Is this linear motion? How fast is the plane moving in respect to the ground?
25 How fast is the plane moving in respect to the ground? Velocity Example 3How fast is the plane moving in respect to the ground?
26 How fast is the plane moving in respect to the ground? Velocity Example 3How fast is the plane moving in respect to the ground?
27 Concept Map: Linear Motion p. 2 when an object moves we observe— which is calculated bycalledThe position changingdistancedisplacementspeedvelocityaccelerationAdding all the legsof the journeyXfinal –x initialTotal distanceTotal timeHow quickly the position changesxfinal –x initialtimeThe rate at which the movement changesvfinal –v initialtime
28 Scalar vs. Vector Scalar - magnitude only and units (e.g. volume, mass, time, speed, distance)magnitude means SIZE,units: like meter, mile, etc.Vector – magnitude, units & direction (e.g. weight, velocity, acceleration)in other words:where is this “thing” pointing?
29 Pictorial Representation An arrow represents a vectorLength = magnitude (size) of vectorDirection = direction of vector
30 Pictorial Representation This arrow could represent a vector of magnitude 10 point to the “right”This arrow could represent a vector of magnitude 5 point to the “left”
31 Get your comp book…Draw an empty Venn Diagram like this on p. 6
32 Label one side scalar, other vector Place these words in the correct space on the diagram:MagnitudeSizeDirectionUnitsDistanceDisplacementSpeedvelocityAccelerationMassWeight12 cm47 kg (mass)470 Newtons (weight)50 meters50 meters West25 m/s25 m/s toward home25 m/s away from home10 m/s210 m/s2 toward the ground
33 AccelerationChange in velocity divided by the change in time
34 Acceleration Great animation showing acceleration: Changing velocity (not constant) means an acceleration is presentAcceleration is the rate of change of the velocity (how fast the velocity changes)Units: m/s2 (SI)other examples: cm/s2ft/s2
35 Average Acceleration Vector quantity When the sign of the velocity and the acceleration are the same (either positive or negative), then the speed is increasingWhen the sign of the velocity and the acceleration are in the opposite directions, the speed is decreasing
36 Relationship Between Velocity & Acceleration Uniform velocity (shown by red arrows maintaining the same size)Acceleration equals zero
37 Relationship Between Velocity & Acceleration Velocity and acceleration are in the same directionAcceleration is uniform (blue arrows maintain the same length)Velocity is increasing (red arrows are getting longer)Positive velocity and positive acceleration
38 Relationship Between Velocity & Acceleration Acceleration and velocity are in opposite directionsAcceleration is uniform (blue arrows maintain the same length)Velocity is decreasing (red arrows are getting shorter)Velocity is positive and acceleration is negative
39 Let’s do a Frayer for acceleration in your comp book: How to calculate:Definition:Wait for the next slideHow to remember:Don’t confuse this with:
40 Acceleration Example 1(solve this problem in the Frayer section…)A car is moving at a speed of 35.8 m/s. If it takes 2.0 s to come to a complete stop, what acceleration would it have?LIST (3) Equation(2) LABEL w/units (4) Solve
41 Acceleration Example 2A car is said to go "zero to sixty in six point seven seconds". What is its acceleration in m/s2?LIST (3) Equation(2) LABEL w/units (4) Solve
42 Acceleration Example 3The driver from the previous problem can't release his foot from the gas pedal. (The gas pedal is also known as the accelerator. Coincidence? I think not.) How many additional seconds would it take for the driver to reach 80 mph? (assuming the acceleration hasn't changed)?LIST (3) Equation(2) LABEL w/units (4) Solve