Objects in motion - 03 Acceleration

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Year 10 Physics unit looking at acceleration.

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Objects in motion - 03 Acceleration

  1. 1. OBJECTS IN MOTION. 03. Acceleration. Ian Anderson Saint Ignatius College Geelong
  2. 2. WHAT IS ACCELERATION? When a car takes off from the traffic lights it will increase its speed until it reaches the speed limit. Acceleration is described as the rate at which speed changes. The quicker the car increases its speed, the greater its acceleration. Source: Sharwood (2006)
  3. 3. CALCULATING ACCELERATION. Acceleration = the rate of change of speed. Acceleration = π‘β„Žπ‘Žπ‘›π‘”π‘’ 𝑖𝑛 𝑠𝑝𝑒𝑒𝑑 π‘β„Žπ‘Žπ‘›π‘”π‘’ 𝑖𝑛 π‘‘π‘–π‘šπ‘’ = π‘“π‘–π‘›π‘Žπ‘™ 𝑠𝑝𝑒𝑒𝑑 βˆ’ π‘–π‘›π‘–π‘‘π‘–π‘Žπ‘™ 𝑠𝑝𝑒𝑒𝑑 π‘‘π‘–π‘šπ‘’ π‘‘π‘Žπ‘˜π‘’π‘› π‘Ž = βˆ†π‘  βˆ†π‘‘ π‘Ž = (𝑣 βˆ’ 𝑒) 𝑑
  4. 4. CALCULATING ACCELERATION. Acceleration is measured in units of ο‚— metres per second per second (m/s/s), or ο‚— metres per second squared (m/s2 or ms-2). If an object slows it is decelerating. Deceleration is negative acceleration. Source: http://oneinamillionsophie.blogspot.com.au
  5. 5. CALCULATING ACCELERATION. In a 100m sprint, Usain Bolt is able to reach a speed of 12 m/s in 6 s. What is his acceleration? Acceleration = π‘β„Žπ‘Žπ‘›π‘”π‘’ 𝑖𝑛 𝑠𝑝𝑒𝑒𝑑 π‘β„Žπ‘Žπ‘›π‘”π‘’ 𝑖𝑛 π‘‘π‘–π‘šπ‘’ = (𝑣 βˆ’ 𝑒) 𝑑 v = 12 m/s u = 0 m/s t = 6 s Source: http://www4.uwsp.edu/physastr/kmenning/Phys203
  6. 6. CALCULATING ACCELERATION. Acceleration = π‘β„Žπ‘Žπ‘›π‘”π‘’ 𝑖𝑛 𝑠𝑝𝑒𝑒𝑑 π‘β„Žπ‘Žπ‘›π‘”π‘’ 𝑖𝑛 π‘‘π‘–π‘šπ‘’ = (𝑣 βˆ’ 𝑒) 𝑑 v = 12 m/s u = 0 m/s t = 6 s Acceleration = (12 βˆ’0) 6 = 2 m/s2 Source: http://www4.uwsp.edu/physastr/kmenning/Phys203
  7. 7. CALCULATING ACCELERATION. If the speed of a car changed from 0 to 60 km/h in 6 s, what was its acceleration (in km/h/s)? Acceleration = π‘β„Žπ‘Žπ‘›π‘”π‘’ 𝑖𝑛 𝑠𝑝𝑒𝑒𝑑 π‘β„Žπ‘Žπ‘›π‘”π‘’ 𝑖𝑛 π‘‘π‘–π‘šπ‘’ = (𝑣 βˆ’ 𝑒) 𝑑 v = 60 km/h u = 0 km/h t = 6 s Source: http://www.lefrelonvert.com/2010/09/elvis-blu- ray-collection/
  8. 8. CALCULATING ACCELERATION. Acceleration = π‘β„Žπ‘Žπ‘›π‘”π‘’ 𝑖𝑛 𝑠𝑝𝑒𝑒𝑑 π‘β„Žπ‘Žπ‘›π‘”π‘’ 𝑖𝑛 π‘‘π‘–π‘šπ‘’ = (𝑣 βˆ’ 𝑒) 𝑑 v = 60 km/h u = 0 km/h t = 6 s Acceleration = (60 βˆ’ 0) 6 = 10 km/h/s Source: http://www.lefrelonvert.com/2010/09/elvis-blu- ray-collection/
  9. 9. ACCELERATION AND GRAPHS. The gradient of a speed-time graph gives you the rate of acceleration. ο‚— A steep speed-time graph indicates a higher acceleration than a graph with a lesser slope. Source: Rickard et al. (2006)
  10. 10. ACCELERATION AND GRAPHS. A car accelerates from rest until it reaches 13 m/s after 5 s. It then continues at that speed for 45 s before it approaches a red traffic light. The driver then slows the car down until it stops at the red light 10 s later. Source: Sharwood (2006)
  11. 11. ACCELERATION AND GRAPHS. What was the car’s acceleration ο‚— in the first 5 s? ο‚— between 5 & 50 s? ο‚— between 50 & 60 s? Source: Sharwood (2006)
  12. 12. ACCELERATION AND GRAPHS. ο‚’ The areas under the graph lines tell us the distance travelled by the car in each time period. ο‚’ The area under the whole graph tells us the distance between the two traffic lights. Source: Sharwood (2006)
  13. 13. ACCELERATION AND GRAPHS. What was the distance covered by the car ο‚— in the first 5 s? ο‚— between 5 & 50 s? ο‚— between 50 & 60 s? ο‚— for the whole 60 s? Source: Sharwood (2006)
  14. 14. BIBLIOGRAPHY. Rickard, G., Phillips, G., Ellis, J., Jeffery, F., & Roberson, P. (2006). Science Dimensions 4: Coursebook. Melbourne: Pearson Education Australia. Sharwood, J. (Ed.). (2006). Science Edge 4. Melbourne: Thomson Learning.
  15. 15. http://SICkScience10.wikispaces.com/

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