MOTION Coach Dave Edinger J. C. Booth Middle School Physical Science (8A)

Start & Stop Time 1 second. Stop & Reset Time 10 seconds. Stop & Reset What is the shortest amount of time you can measure? Reset

1. What is motion? A way of describing how fast something is moving Our definition: the state in which one object’s distance from another is changing.

2. What is a reference point? A point that motion is measured against Usually a stationary object

3. How do you know if an object is in motion? An object is in motion if it changes position relative to a reference point

it depends on your reference point! Are you in motion? it depends on your reference point! 2 minutes

4. What is the difference between distance and displacement? Distance is the total length of the actual path between two points. Displacement is the length and direction of a straight line between starting and ending points.

What is my displacement?

Place 2 dots on a plate 4 cm apart. Place a spoonful of honey on one dot. Lift one side of the plate and time how long it takes to reach the other dot/line.

5. What is speed? The distance an object travels per unit of time. miles per hour miles/hour

6. How do you calculate speed? Divide the distance the object traveled by the amount of time it takes to travel that distance.

…some useful speeds Growing fingernails = 4 cm/year Walking speed = 3 miles/hr or 1.3 m/s Driving speed = 60 miles/hr or 26 m/s Earth’s revolution = 30 km/s Speed of light = 300,000 km/s

Example: 120 miles in 2 hours S = D S = 120 miles S = 60 miles/hour Road Trip! Example: 120 miles in 2 hours S = D S = 120 miles S = 60 miles/hour T 2 hours

7. Why would you calculate average speed? Because most moving objects do not move at a constant speed. Think about biking uphill and downhill

…or think of traffic

8. How do you calculate average speed? Average speed = Total Distance Traveled Total Time of Travel

Traffic! Example: 32 km for 2 hours, then 13 km for 1 hour Total distance = 32 km + 13 km = 45 km Total time = 2 h + 1 hr = 3 hr Average speed = 45 km ÷ 3 hr = 15 km/hr

9. What is instantaneous speed? The rate at which an object is moving at a given instant in time. …or what your speedometer says!

10. What is velocity? Speed in a given direction Ex: 20 miles/hour West A storm is moving 25 km/h. Should you prepare?

11. How can you describe changes in velocity? Change in velocity may be due to change in speed, change in direction, or both!

12. How do you graph speed? By a distance versus time graph! X-axis = time Y-axis = distance Slope = slant of line y Distance (m) 50 X 5 Time (min)

13. How can you interpret graphs of distance versus time? The slope represents speed Slope = slant of line = speed! Steep = Fast! Shallow = Slow!

What if it is flat? Flat = Not moving!

Walk to flag pole with a partner. Distance is 50 meters. Time yourself: Slow : Normal : Fast :

Calculate YOUR speeds: Make sure all time is in seconds. Remember that there are 60 seconds in 1 minute (1:07.23 = 67.23 seconds) Use your speed formula S = D/T Use a calculator. Round answer to tenths place.

Graph your 3 speeds! Time on X axis; Distance on Y axis.