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Do Now: What are the two meanings of the word “time” in physics?. Tick tock, tick tock, tick tock. Time…. It can mean either a moment in time like when you as, “What time is it?” OR…. It can mean a quantity of time, for example how long did something take to occur?
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Do Now: What are the two meanings of the word “time” in physics? Tick tock, tick tock, tick tock
Time…. • It can mean either a moment in time like when you as, “What time is it?” OR…. • It can mean a quantity of time, for example how long did something take to occur? We use the second (sec) as our basic unit of time.
Speed & constant speed • What is the difference? • Speed describes movement from one place to another over time; we say it’s the distance divided by time. • Constant speed is a maintained speed that does not change. This means the same distance is traveled every second.
Why do we use v? V stands for velocity, which indicates that you know direction as well as speed.
What are the units? • Meters per second • Kilometers per hour • Centimeters per second • Miles per hour • Inches per second • Feet per minute
Now let’s practice… • What is the average speed of a car that traveled 300.0 miles in 5.5 hours? • A bicyclist, traveling at 22 miles per hour, rides a total of 44 miles. How much time, in hours, did it take? • How far can a person run in 15 minutes if he or she runs at an average speed of 16km/hr? Hint make sure your time is in the same units! • You ride your bike for a distance of 30 km. You travel at a speed of 0.75 km/minute. How many minutes does this take?
Answers: • speed = distance / time…. 300 miles/5.5 hours = • Time = distance /speed 44 miles/22 miles/hour 3. Distance = speed * time 15 minutes * 1 hour/60 minutes = 0.25 hours 16 km/hour * 0.25 hours = • Time = distance /speed 30 km / 0.75 km/minute
homework • Page 21 numbers 3, 4, and 5