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Published byMax Shire Modified over 2 years ago

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MOTION Three featured concepts are: Speed Velocity Acceleration

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MATH CONNECTION These are called rates The units in Math may have been BE Like Feet per second; Miles per hour Ft./Sec. OR mi./hr. or mph

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In Science we use SI UNITS Meters per second; kilometers per hour m/s OR km/h or kph There are as may rates as there are units: cm/s; mm/h; even mm/y or cm/century It all depends on the topic of study.

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What’s the dif? Glad you asked: Speed is a rate of distance over time or just called magnitude like: 5 m/s or 25 mph. VOLOCITY is the rate of distance over time but indicates a direction! Magnitude + direction: 5m/s -north or 25 mph-south

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So can you tell the difference? TRY SOME: 15 m/s 100 mph - north 2.34 cm/s 17.4 ft./hr.-up 25 kph- south km/h

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How about Acceleration? Acceleration is defined as a change in speed of velocity over time. More complicated for sure. a =∆v / ∆t We have to check out the white board to see this broken down!!!!

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UNITS for ACCELERATION Because it involves a double division the units of course are complicated usinfg two speeds together. Examples of acceleration units are: m/s/s (not new) remember 9.8 m/s/s? or m/s 2 Ft./sec./sec. or ft./sec. 2 Km/h/s m/h/s Basically any distance divided by a time divided by another time: any d/t/t defines an acceleration unit of measure!

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Sample Speed Problem #1 It takes a car 30 seconds to go 90 meters. What is the speed? Menu: V = d/t (means d ÷ t) V= ? = 90m/ 30s d = 90 m V = 3m/s t = 30 s

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PROBLEM # 2 A car can travel a speed of 3 m/s over a time of 30 seconds how far would it go? Menu: d = vt (means v X t) d = ? = (3 m/s) (30 s) (cross cancel s) v = 3 m/s d = 90 m t = 30 s

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PROBLEM # 3 How long will it take a car to go 90 meters at a speed of 3 m/s? Menu: t = d/v ( means d ÷ v ) t = ? = 90 m / 3 m/s d = 90 m [t= 30 s] v = 3 m/s

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ACCELERATION Sample Problem: A car’s speedometer indicates a speed of 30 kph and after 10 seconds of time the driver notices the speed is now 90 kph. What is the car’s acceleration? a = ? a = v f - v i t v f = 90 km/h = 90 km/h - 30 km/h 10 s v i = 30 km/h = 60 km/h 10 s t= 10 s a = 6 km/h/s

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Deceleration Sample Problem: A truck is going 75 kph and 5 seconds later it is clocked going 55 kph. What is the deceleration. HINT: Use the same equation (formula) then change the a to (–a) after finding the answer. a= ?a = V f - V i t V f = 55 kph = 55 kph – 75 kph 5s V i = 75 kph = - 20 kph 5s t = 5s a = -4kph/s -a = 4 kph/s

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