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## Describing Motion

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**Motion**• Sit very still. Do not move. • In what ways are you moving? Changing position?**Motion**• All motion is relative. • Must be a frame of reference. • MOTION is a change in position of an object with respect to time**Motion**• How far an object moves is DISTANCE • Meters is the SI unit of length or distance 50 m**Motion**• DISPLACEMENT is the distance and direction of an objects change in position from the starting point 50 m North**Speed**• Speed is the distance an object travels per a unit of time. d distance Speed = S = t time**Describing Motion**• Average speed- total distance traveled divided by total time • It takes me 13 hours to travel 1440 kilometers. My average speed is 110.8 km/hr • Instantaneous speed- speed at a particular point in time, like when you look down at your speedometer. • An object that is speeding up or slowing down, its instantaneous speed is changing**Graphing Motion**Slope of the line in a distance vs time graph will give you the object’s speed**Speed**http://www.google.com/imgres?q=distance+over+time+graph&num=10&hl=en&safe=active&gbv=2&biw=1024&bih=605&tbm=isch&tbnid=oQWNuVo_FwpgiM:&imgrefurl=http://www.tutorvista.com/content/physics/physics-i/motion/distance-time.php&docid=SHYo4Afu8tqUoM&w=491&h=337&ei=Z21fTvmHOdKCsgL5sszzCQ&zoom=1&iact=hc&vpx=142&vpy=97&dur=23207&hovh=186&hovw=271&tx=116&ty=146&sqi=2&page=1&tbnh=130&tbnw=190&start=0&ndsp=12&ved=1t:429,r:0,s:0**Speed**http://www.syossetistops.org/index.php?m=UserPages&e=viewPage&id=1424**Velocity**• Velocity is the speed and direction of motion of an object in motion. • An up and a down escalator moving at the same speed have different velocities because they are travelling in opposite directions • A car driving in a circle with a constant speed of 100 km/hr has a constantly changing velocity**Velocity**• These cars are travelling at the same speed. Do they have the same velocity?**Velocity**• Velocity is the speed and direction of motion of an object in motion. • A change of velocity may be a change of speed. • Or a change of velocity may be constant speed with a change of direction.**Practice Problems**• A car is moves 20 meters is 4 seconds. What is its speed? • A car is moving 25 m/s for 8 seconds. How far did the car travel?.**Practice Problems**• A group of bike riders took a 4.0 hour trip. During the first 3.0 hours, they traveled a total of 50. kilometers but during the last hour they traveled only 10. kilometers. What was the group's average speed for the entire trip?**Practice Problems**• During which interval was the cart at rest?**Practice Problems**• During which interval was the cart moving in a negative direction?**Practice Problems**• During which of these two intervals, BC and DE, was the cart traveling at a faster rate?