Speed and Velocity 11 2 Speed Speed The

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Speed and Velocity 11. 2

Speed and Velocity 11. 2

Speed Speed: The ratio of the distance an object moves To the amount of

Speed Speed: The ratio of the distance an object moves To the amount of time the object moves SI Unit of meters per second (m/s) Average Speed: Example Total distance divided by total time While traveling on vacation, you measure the times and distances traveled. You travel 35 kilometers in 0. 4 hours, followed by 53 kilometers in 0. 6 hour. What is your average speed? Instantaneous Speed: In this trip, did you go 88 km/hr the ENTIRE time? Your car’s speedometer measures instantaneous speed 35 km in 0. 4 hrs A 53 km in 0. 6 hrs B C

Graphing Motion A distance-time graph is a good way to describe motion Imagine you

Graphing Motion A distance-time graph is a good way to describe motion Imagine you measure the distance a car went every other second Here’s what you record for car A: For car B: Can you see this: What would the STEEPNESS (slope) of these lines mean: The slope of a line on a distance-time-graph is SPEED Car A covers 100 meters every second 100 m/s Car B covers 100 meters every 2 seconds 100 m / 2 s = 50 m/s

Graphing Varying Speed What does it seem this car is doing: He’s going fast

Graphing Varying Speed What does it seem this car is doing: He’s going fast from t = 0 s to t = 3 s He’s stopped from t = 3 s to t = 7 s He’s going slow from t = 7 s to t = 10 s How fast is he going? Fast = 200 m/s How slow is he going? Slow = 50 m/s

Velocity Caracas is about 200 km away from here You could get there in

Velocity Caracas is about 200 km away from here You could get there in 2 hrs Speed? 100 If you go 100 km/h, will you get to Caracas? You need a direction What was the difference between Distance Displacement One km/h of them has a direction Same here: Speed Velocity = speed + direction

Combining Velocities Sometimes the motion of an object involves more than one velocity Like

Combining Velocities Sometimes the motion of an object involves more than one velocity Like a boat in a fast moving river: If the river carries a current of 5 km/h East A boat with its motor set for 12 km/h East How fast does the boat look like it is going from the ground? Vector addition, X + Y = Z 17 km/h 5 km/h 12 km/h

Combining Velocities Sometimes the motion of an object involves more than one velocity Like

Combining Velocities Sometimes the motion of an object involves more than one velocity Like a boat in a fast moving river: If the river carries a current of 5 km/h East A boat with its motor set for 12 km/h West How fast does the boat look like it is going from the ground? Vector addition, X + Y = Z 7 km/h 5 km/h 12 km/h

Combining Velocities Sometimes the motion of an object involves more than one velocity Like

Combining Velocities Sometimes the motion of an object involves more than one velocity Like a boat in a fast moving river: If the river carries a current of 3 km/h East A boat with its motor set for 4 km/h North How fast does the boat look like it is going from the ground? addition, X + Y = Z m/ h Vector 5 k 4 km/h 3 km/h