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Fastest Ball in Sports !

Fastest Ball in Sports !. Speed and acceleration. Motion. Distance ( d ) – describes how far an object has travelled from a starting point. Units for distance are metres (m) or kilometres (km) Eg. Christchurch is 360km from Dunedin. Motion.

macaulay-velazquez
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Fastest Ball in Sports !

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  1. Fastest Ball in Sports !

  2. Speed andacceleration

  3. Motion • Distance (d ) – describes how far an object has travelled from a starting point. • Units for distance are metres (m) or kilometres (km) • Eg. Christchurch is 360km from Dunedin

  4. Motion • Time ( t ) – describes how long an object takes to reach its end point. • Units for time are seconds (s), minutes (min) and hours (hr) • Eg. It takes 17.5 min to get to school.

  5. Motion • Speed(v) – used to describe how fast an object is moving. • Speed is often referred to as velocity (v). • Units for speed are measured as distance per unit of time m/s km/hr km/s.

  6. Types of v • Instantaneous speed (v) – how fast an object is moving at a given point in time. • Average speed(vav) – how fast an object is moving over the entire journey.

  7. Average Speed • To work out the speed of an object you need to know: d and t

  8. Calculating Average Speed • The units for speed depends on the units for distance and time. d average speed = distance travelled time taken t vav

  9. Speed Formula Triangle

  10. Try This ! #1 • A boy takes 1 hour to travel from his home to the cinema, a distance of 10 km. Calculate his average speed in km/hr. Vav = = = 10 km/hr d t vav d t 10 km 1 h Cover the quantity to be calculated.

  11. Try This ! #2 • A boy takes 1 hour to travel from his home to the cinema, a distance of 10 km. Calculate his average speed in m/s. Vav = = = 2.8 m/s d t vav d t 10 000 m 3 600 s Cover the quantity to be calculated.

  12. Try This ! #3 • A family set off from home and walk at an average speed of 3.6 km/h. How far will they travel in two hours? d = Vavxt = 3.6 km/hx 2 h = 7.2 km d t vav Cover the quantity to be calculated.

  13. Try This ! #4 • How long would it take a woman to walk 10 km, if her average speed was 5.4 km/h? t = = = 1.85 h d t vav d Vav 10 km 5.4 km/h Cover the quantity to be calculated.

  14. Speedy Snowmobiles • Go to website.

  15. Graphing Speed • This graphing experiment shows an animation of a car travelling along a straight road. • Copy the results table shown on the next slide and complete it as the movie is played. • Record the distance the car has travelled every five seconds. • Plot a graph of your results.

  16. Graphing Speed

  17. Graphing Speed

  18. Graphing Speed Results

  19. Graphing Speed

  20. The speed of the car is changing – the graph is not flat. The slope of the graph is less steep as the car begins to slow down. The car has stopped. The graph is flat – the distance of the car from the start point is not changing. The graph is straight – there is no change in speed. The car is going fast but at a constant speed. The graph is straight in this part of the journey. The car is starting to move. The curve shows that the speed is changing. The curve is upwards as the car accelerates at the start of the journey. Graphing Speed

  21. Slope of Distance-Time Graphs • The speed of the car can be calculated by looking at the slope (gradient) of the distance/time graph. • Speed is “distance travelled” divided by “time taken”. • These values can be read off the distance/time graph at different points, and this is the same as the gradient of the graph.

  22. Graphing Speed The car has travelled from 200m to 800m = 600m. It took from 17s to 36s to travel this distance = 19 s. So the speed at this point = 600m/19s = 31.6m/s.

  23. Acceleration • Acceleration (a)– shows the change in speed over a period of time. • Acceleration can be both positive (acceleration) and negative (deceleration).

  24. Calculating Acceleration • The units for acceleration depends on the units for speed and time. ∆V acceleration = final speed - initial speed time taken ∆t a

  25. Try This ! #5 • A car speeds up from a stop light to a speed of 15.3 m/s in just 4 seconds. Calculate the acceleration of the car. a = = = 3.8 m/s/s or m/s2 ∆V ∆t a ∆V ∆t 15.3 m/s 4 s Cover the quantity to be calculated.

  26. Try This ! #6 • As she climbs a hill, a cyclist slows down from 7 m/s to 3 m/s in 10 seconds. What is her acceleration?. a = = = - 0.4m/s2 ∆V ∆t a ∆V ∆t - 4 m/s 10 s Cover the quantity to be calculated.

  27. Try This ! #7 • While traveling along a highway a truck goes from 100 km/hr to 60 km/hr in 8 seconds. What is the truck’s acceleration?. a = = = - 1.4 m/s2 ∆V ∆t a ∆V ∆t 8 s - 40 km/h - 11.1 m/s Cover the quantity to be calculated.

  28. Graphing Acceleration • The slope of a speed-time graph gives an objects acceleration.

  29. Graphing Acceleration • The area under the graph gives us the distance travelled

  30. Acceleration vs. Deceleration

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