Speed of 120 km/h (about 75 mi/h). For a male athlete, the ball may travel even faster. A fast-pitch pitcher uses a “windmill” motion to throw the ball. This is a different technique than other softball pitches
Download 45.21 Kb.
|
- Navigate this page:
- Average Speed
- Instantaneous Speed
- Summary
SpeedDid you ever play fast-pitch softball? If you did, then you probably have some idea of how fast the pitcher throws the ball. For a female athlete like the one in the opening image, the ball may reach a speed of 120 km/h (about 75 mi/h). For a male athlete, the ball may travel even faster. A fast-pitch pitcher uses a “windmill” motion to throw the ball. This is a different technique than other softball pitches, and it explains why the ball travels so fast. How fast or slow something moves is its speed. Speed determines how far something travels in a given amount of time. The SI unit for speed is meters per second (m/s). Speed may be constant, but often it varies from moment to moment. Average SpeedEven if speed varies during the course of a trip, it’s easy to calculate the average speed by using this formula: speed = distance time. For example, assume you go on a car trip with your family. The total distance you travel is 120 miles, and it takes 3 hours to travel that far. The average speed for the trip is: 120 mi 3 h = 40 mi/h Instantaneous SpeedWhen you travel by car, you usually don’t move at a constant speed. Instead you go faster or slower depending on speed limits, traffic lights, the number of vehicles on the road, and other factors. For example, you might travel 65 miles per hour on a highway but only 20 miles per hour on a city street (see the pictures in the Figure below.) You might come to a complete stop at traffic lights, slow down as you turn corners, and speed up to pass other cars. Therefore, your speed at any given instant, or your instantaneous speed, may be very different than your speed at other times. Instantaneous speed is much more difficult to calculate than average speed. 
Calculating Distance or Time from Speed If you know the average speed of a moving object, you can calculate the distance it will travel in a given period of time or the time it will take to travel a given distance. To calculate distance from speed and time, use this version of the average speed formula given above: distance = speed × time For example, if a car travels at an average speed of 60 km/h for 5 hours, then the distance it travels is: distance = 60 km/h × 5 h = 300 km To calculate time from speed and distance, use this version of the formula:
How fast or slow something moves is its speed. The SI unit for speed is meters per second (m/s). Average speed is calculated with the formula speed = distance time Speed may be constant, but often it varies from moment to moment. Speed at any given instant is called instantaneous speed. It is much more difficult to calculate than average speed. Distance or time can be calculated by solving the average speed formula for distance or time. Speed Practice 1. How fast or slow something moves is its _____. 2. True or false: Speed determines how far something moves in a given amount of time. 3. The SI unit for speed is a) cm/s. b) m/s. c) m/h. d) km/h.
a) 6 m/h b) 10 m/h c) 20 m/h d) 60 m/h
a) distance = speed/time. b) distance = speed x time. c) distance = time/speed. d) none of the above
a) time = distance/speed. b) time = distance x speed. c) time = speed/distance. d) none of the above 9. If you walk at an average speed of 5 km/h for 30 minutes, how far will you walk? 10. If you run at an average speed of 10 m/h, how long will it take you to run 2.5 miles? Directory: cms -> lib04 -> VA01000023 -> Centricity -> Domain lib04 -> Neptune high school lib04 -> [3rd Grade Writing Scope and Sequence] lib04 -> Special Events Date lib04 -> Lovett Elementary’s 2014-2015 Accelerated Reader Policy Domain -> Strategies for Enhancement and Intervention Differentiation of Instruction lib04 -> W. C. Handy composed the blues classic "St. Louis Woman" lib04 -> Chapter summary lib04 -> In 1890 what device did the us census use to tabulate the Census? What company built it and how did it work? lib04 -> Luke: the brain Danielle: she never stands up for herself Anna Download 45.21 Kb. Share with your friends:
|