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Ch 11 Motion

Ch 11 Motion. Please define these vocabulary words:. Distance Speed Average speed Instantaneous speed Velocity Acceleration Free fall Constant acceleration. 11.1: Distance and Displacement. Distance…. length of a path between two points

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Ch 11 Motion

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  1. Ch 11 Motion

  2. Please define these vocabulary words: • Distance • Speed • Average speed • Instantaneous speed • Velocity • Acceleration • Free fall • Constant acceleration

  3. 11.1: Distance and Displacement

  4. Distance… • length of a path between two points • When an object moves in a straight line, the distance is the length of the line connecting the object’s starting point and its ending point.

  5. Measuring Distance • The SI unit for measuring distance is the meter (m). • For very large distances, it is more common to make measurements in kilometers (km). • Distances that are smaller than a meter are measured in centimeters (cm).

  6. Displacement… • DIRECTION from the starting point and the LENGTH of a straight line from the starting point to the ending point.

  7. Distance vs Displacement • How are distance and displacement different? • Distance=length • Displacement=directionand the length

  8. Warm Up 3/24/09Fill in the Blanks…( write complete statements) • EVERYTHING is in constant _ _ _ _ _ _ . • Distance is the _ _ _ _ _ _ between a starting point and an ending point. • Displacement involves the _ _ _ _ _ _ between two points and the _ _ _ _ _ _ _ _ _ it is traveling. • In order for an object to move, a _ _ _ _ _ has to act upon it. • The _ _ _ _ of an object affects how much force is required to move it.

  9. 11.2: Speed and Velocity

  10. Speed -The ratio of the distance an object moves to the amount of time the object moves. -The SI unit of speed is meters per second (m/s). -Two ways to express the speed of an object are average speed and instantaneous speed.

  11. Formula used to Calculate Speed Speed=distance/time S=d/t Distance (m)/Time (s)=Speed (m/s)

  12. Average Speed vs Instantaneous Speed • How are instantaneous speed and average speed different? • Average speed is computed for the entire duration of a trip, and instantaneous speed is measured at a particular instant.

  13. Average Speed • Average speed, is the total distance traveled, d, divided by the time, t, it takes to travel that distance.

  14. Instantaneous Speed -Instantaneous speed, v, is the rate at which an object is moving at a given moment in time. -The speedometer in a car measures the car’s instantaneous speed. -Note the scale markings are given both in km/h and miles per hour, mph.

  15. Graphing Motion • Speed can also be determined by looking at a distance-time graph. • The slope of a line on a distance-time graph is the speed of the object. • Slope is the change in the vertical axis value divided by the change in the horizontal axis value. • Steeper slope means faster speed.

  16. Distance-Time Graphs

  17. Distance-Time Graphs

  18. Distance-Time Graphs

  19. Velocity • Velocity is a description of BOTH speed and direction of motion. • The unit for velocity is meters per second.

  20. Practice • A football field is about 100 m long. If it takes 20 seconds to run its length, how fast (what speed) were they running?

  21. Practice • The pitcher’s mound in baseball is 85 m from the plate. It takes 4 seconds for a pitch to reach the plate. How fast is the pitch?

  22. Practice • If you drive at 100 km/hr for 6 hours, how far will you go?

  23. Practice • Every summer I drive to Michigan. It is 3900 km to get there. If I average 100 km/hr, how much time will I spend driving?

  24. Practice • If a delivery truck drives 537 miles in 7 hours, how fast was he driving?

  25. 11.3: Acceleration

  26. Velocity • Velocity is a description of BOTH speed and direction of motion. • The unit for velocity is meters per second.

  27. What is acceleration? • The rate at which velocity changes. • In science, acceleration applies to any change in an object’s velocity.

  28. What is acceleration? • Acceleration can be caused by positive (increasing) change in speed or by negative (decreasing) change in speed. • Deceleration is an acceleration that slows an object’s speed. • The unit for acceleration is meters per second squared (m/s2).

  29. Free Fall • Free fall isthe movement of an object toward Earth solely because of gravity. • Objects falling near Earth’s surface accelerate downward at a rate of 9.8 m/s2. • Each second an object is in free fall, its velocity increases downward by 9.8 meters per second.

  30. Constant Acceleration • Constant acceleration is a steady change in velocity. • The velocity of an object moving in a straight line changes at a constant rate when the object is experiencing constant acceleration.

  31. Calculating Acceleration • You calculate acceleration for straight-line motion by dividing the change in velocity by the total time. • Acceleration is the rate at which velocity changes. Vi is the initial velocity, vf is the final velocity, and t is total time.

  32. Calculating Acceleration If the velocity increases, the acceleration is positive. If the velocity decreases, the acceleration is negative. • If you are coasting downhill on a bicycle, your velocity increases, and your acceleration is positive. • If you continue coasting on level ground, your velocity decreases, and your acceleration is negative.

  33. Practice • A parachute on a racing dragster opens and changes the speed of the car from 85 m/s to 45 m/s in a period of 4.5 seconds. What is the acceleration of the dragster?

  34. Practice • A car traveling at a speed of 30.0 m/s encounters an emergency and comes to a complete stop. How much time will it take for the car to stop if it decelerates at -4.0 m/s2?

  35. Practice • A helicopter’s speed increases from 25 m/s to 60 m/s in 5 seconds. What is the acceleration of this helicopter?

  36. Practice • After traveling for 6.0 seconds, a runner reaches a speed of 10 m/s. What is the runner’s acceleration?

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