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Speed, velocity and acceleration

Speed, velocity and acceleration. Physics 100 Chapter 2. speed. distance traveled elapsed time. speed = v =. Hawaii Kai  Haleiwa In one hour. 50km 1 hr. v =. = 50 km/hr. 50km. This is the average speed over 1 hour. For shorter time intervals it can be higher or lower.

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Speed, velocity and acceleration

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  1. Speed, velocity and acceleration Physics 100 Chapter 2

  2. speed distance traveled elapsed time speed = v = Hawaii Kai Haleiwa In one hour 50km 1 hr v = = 50km/hr 50km This is the average speed over 1 hour. For shorter time intervals it can be higher or lower.

  3. Earth’s motion around the Sun r=1.5x1011m distance elapsed time 2 p r 2 x 3.14 x 1.5 x 1011m 365 days x 24 hrs/day = V = = 1year 9.4 x 1011 m 8.76 x103 hrs 9.4 x 1011 m 8760 hrs = 1.1x108 m/hr = = = 1.1x105 km/hr  70,000 mi/hr

  4. Velocity = speed + direction 6 months later speed = same different direction v r=1.5x1011m velocity is a “vector”: a quantity that has both magnitude and direction Length of the arrow = speed Direction of arrow same as direction of the motion

  5. Scalars and Vectors Simple numbers: Speed v Temperature T Number + direction Velocity v relative positions r Force F Acceleration a Campus Center r PSB

  6. Acceleration ( changes in v) change in velocity elapsed time acceleration = change in v elapsed time a =

  7. Change in V = 100km/hr Elapsed time = 3 sec change in v elapsed time a = 103 m 100km/hr 3 s = 33 km/hr s = 3600s =3.6x103s 33x103m 3.6x103 sxs = 9.1 m/s2 = “This baby goes from 0 to 100km/hr in only 3 seconds”

  8. Different ways to change V v v Car speeds up a v v screech! Car slows up a

  9. Accelerations (continued) v v Car turns a In all three cases, v changes. Therefore these are all examples of accelerations

  10. Free Fall

  11. t=0 v0=0 dist time 5m 1 s vavg = = = 5m/s 0 + v1 2 v0 + v1 2 v1 2 vavg = = = 5m v1 = 2vavg = 10 m/s t=1s v1=? V1 = 10 m/s

  12. Free-fall acceleration 10m/s change in velocity elapsed time acceleration = 1s 10m/s 1s g a = = 10 m/s2 This is called the “acceleration due to gravity” and given the special symbol: g=10m/s2 Actually g=9.8m/s2. But 10 m/s2 is close enough for us.

  13. Free fall from greater heights t = 0s Total distance V0 = 0 5m 5m t = 1s V1 = 10m/s 15m 20m t = 2s 1 2 gt2 V2 = 20m/s 25m t = 3s 45m V3 = 30m/s 35m t = 4s 80m V4 = 40m/s

  14. Upward toss Total height t = 4s V4 = 0 80m 5m V3 = 10m/s t = 3s 75m 15m 60m V2 = 20m/s t = 2s 1 2 v0t- gt2 25m V1 = 30m/s 35m t = 1s 35m t = 0 V0 = 40m/s 0m

  15. Simple rule for free fallaka: projectile motion When Earth’s gravity is the only force involved: actual height = height for no gravity – ½gt2

  16. Horizontal toss t = 0s t = 1s t = 3s t = 4s t = 2s 5m 20m 45m 80m

  17. t = 4s upward toss t = 3s t = 2s 45m 80m 20m t = 1s 5m t = 0s

  18. dead white European male Shoot the monkey communist

  19. Shoot the DWEM: Slower bullet

  20. Very fast horizontal toss t = 0s t = 1s x= 8km t = 2s x=16km t = 3s x=24km V=8km/s 5m 20m 45m

  21. Orbital motion is free fall

  22. Artificial satellite

  23. Turning car An object free to slide on the dashboard, tries to follow a straight line path

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