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Come on people, this is not rocket science Thursday, October 01, 2015

Oh, Wait

Motion Chapter 6 Section 1

What is Motion? A Change in Position

Motion…

Distance and Displacement Distance – How far you have traveled Distance – How far you have traveled Displacement – How far away it is Displacement – How far away it is

Distance Verses Displacement

Texas Motor Speedway 1.5 mile oval

Distance Vs Displacement If a driver goes 200 laps starting at the start line and finishing at the finish line; If a driver goes 200 laps starting at the start line and finishing at the finish line; What is the distance traveled? What is the distance traveled? What is the displacement? What is the displacement?

Answer The distance traveled is 300 miles (200 laps X 1.5 miles per lap) The distance traveled is 300 miles (200 laps X 1.5 miles per lap) The displacement is zero. (The driver is at the same location he started from.) The displacement is zero. (The driver is at the same location he started from.)

Relative motion An object in motion changes position An object in motion changes position This position is in relation to another object This position is in relation to another object

Speed Two factors determine speed Two factors determine speed –Distance traveled –Time spent traveling –Examples; Miles per hour Miles per hour Feet per second Feet per second Meters per second Meters per second Speed is distance divided by time Speed is distance divided by time

Speed

So…

And…

Constant Speed Cruise control set at 60 MPH Cruise control set at 60 MPH Always at the same speed Always at the same speed Covering one mile every minute Covering one mile every minute –Same distance each time interval Key term CONSTANT! Key term CONSTANT!

Average Speed Total time divided by total distance. Total time divided by total distance. RMS to Six Flags 20 minutes. RMS to Six Flags 20 minutes. 13 miles 20 minutes. 13 miles 20 minutes. Constant Speed? Constant Speed? No… stop signs, freeways, city streets. No… stop signs, freeways, city streets. Different rates of speed. Different rates of speed. This is average speed. This is average speed.

What is Our Speed? 13 miles 13 miles 20 minutes =.33 hours 20 minutes =.33 hours 13 Miles/0.33 Hours = 39.4 M/H or MPH 13 Miles/0.33 Hours = 39.4 M/H or MPH

Velocity What is the difference between velocity and speed? What is the difference between velocity and speed? Velocity has direction, speed does not Velocity has direction, speed does not Remember displacement and distance? Remember displacement and distance? Speed is distance divided by time Speed is distance divided by time Velocity is displacement divided by time Velocity is displacement divided by time

OR… Δ (delta) is science speak for change in something

Calculation A Sprinter runs a 100 meter race in 10 seconds A Sprinter runs a 100 meter race in 10 seconds What is his average velocity? What is his average velocity? Distance is 100 meters Distance is 100 meters Time is 10 seconds Time is 10 seconds 100Meters ÷ 10 Seconds = 10M/S 100Meters ÷ 10 Seconds = 10M/S

Texas Motor Speedway 1.5 mile oval

Velocity vs. Speed If a driver goes 200 laps starting at the start line and finishing at the finish line in 2 Hours If a driver goes 200 laps starting at the start line and finishing at the finish line in 2 Hours What is his speed? What is his speed? What is his velocity? What is his velocity?

Answer Speed Speed 300 Miles (distance)/2 Hours = 150 MPH 300 Miles (distance)/2 Hours = 150 MPH Velocity Velocity 0 (displacement)/2 Hours = 0MPH 0 (displacement)/2 Hours = 0MPH

Acceleration A change in velocity A change in velocity Speeding up or slowing down Speeding up or slowing down Acceleration equals final velocity minus initial velocity divided by time Acceleration equals final velocity minus initial velocity divided by time

OR

Calculation A skateboarder goes from 2 m/s to 8 m/s in 12s. What is his acceleration A skateboarder goes from 2 m/s to 8 m/s in 12s. What is his acceleration Initial velocity = 2m/s Initial velocity = 2m/s Final velocity = 8m/s Final velocity = 8m/s Time is 12s Time is 12s So ΔV = 8m/s - 2m/s = 6m/s So ΔV = 8m/s - 2m/s = 6m/s 6ms ÷ 12s = 0.5m/s/s or 0.5m/s 2 6ms ÷ 12s = 0.5m/s/s or 0.5m/s 2

Calculation Same skateboarder hits a mud hole and goes to a complete stop in 1s. What is his acceleration Same skateboarder hits a mud hole and goes to a complete stop in 1s. What is his acceleration Initial velocity = 8m/s Initial velocity = 8m/s Final velocity = 0m/s Final velocity = 0m/s Time is 1s Time is 1s So… ΔV = 0m/s - 8m/s = -8m/s So… ΔV = 0m/s - 8m/s = -8m/s -8ms ÷ 1s = -8m/s/s or -8m/s 2 -8ms ÷ 1s = -8m/s/s or -8m/s 2

Turning Remember velocity has direction. Remember velocity has direction. So a change in direction is also acceleration So a change in direction is also acceleration

Texas Motor Speedway 1.5 mile oval

Question If a racecar is traveling at a constant speed at Texas Motor Speedway, is it accelerating? If a racecar is traveling at a constant speed at Texas Motor Speedway, is it accelerating? Yes, on the turns. Yes, on the turns.

Three Ways to Accelerate 1. Increase velocity 2. Decrease velocity 3. Change direction

THE END