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What is speed?

What is speed?. Watch the toy car: (pull back car) What did you see? The car changed positions. How does what you saw define the term SPEED? How fast an object is moving or changing positions. Speed is the rate at which distance is covered. Why is speed referred to as a RATE?

stephanie-rokos
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What is speed?

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  1. What is speed?

  2. Watch the toy car: (pull back car) • What did you see? • The car changed positions. • How does what you saw define the term SPEED? • How fast an object is moving or changing positions. • Speed is the rate at which distance is covered. • Why is speed referred to as a RATE? • Rate is a clue that something is changing in a time period. • Heart rate • Interest rate • Dropout rate

  3. What is a SCALAR QUANTITY? • A quantity in which direction is either n/a or not specified. • temperature • What are the units of speed? • any distance unit / any time unit • mph • km/h • cm/day • What are the most common units we will use for speed? • meters per second m/s • kilometers per hour km/h

  4. Examples of speeds:

  5. The speed equation: • In words: • speed=distance / time • In symbols: • s= d/t • The wheel: • Cover the unknown d s t

  6. Let’s look at other types of speed: • How can you tell a car’s speed at a given instant in time? • look at the speedometer • What is this type of speed called? • instantaneous speed • Example-Bus ride to school this morning

  7. In riding the bus this morning, the driver has an idea of how long it will take to cover a certain distance. The bus did not travel the same speed during the whole trip. What is the type of speed the driver is concerned with? • AVERAGE SPEED • What is the formula for this type of speed? • average speed = total distance / total time • s = dt/tt • What does the bar over the s indicate? • average

  8. Watch your teacher: • How is this type of speed different than what you have seen so far? • covered same distance with each step • Watch the car: (battery operated car) • What would you call this type of speed? • constant speed • equal distances in equal amounts of time

  9. How does the driver of an automobile ensure they are traveling at this type of speed? • Cruise control • What are the parts of a car that control speed? • gas pedal (accelerator) • brake pedal (decelerator) • NO MATTER WHAT TYPE OF SPEED WE ARE TALKING ABOUT WE ARE STILL INTERESTED IN THE CHANGE OF POSITION IN A GIVEN AMOUNT OF TIME.

  10. Sample Problems: • 1. What is the average speed of a marble that rolls 45 centimeters in 5 seconds? • G • d= 45cm • t= 5s • U • s =? • E • s = dt/tt

  11. S • s = 45cm / 5s = 9cm/s • S • s = 9cm/s

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