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Science 10

Science 10. Aim: Calculating Conversions, Displacement, Time, speed and velocity. Agenda. Conversion examples Conversion worksheet Lunch – extra help time Displacement and velocity notes Homework: read p. 137-154 (acceleration and velocity)) Next class. Calculating Displacement.

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Science 10

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  1. Science 10 • Aim: Calculating Conversions, Displacement, Time, speed and velocity

  2. Agenda • Conversion examples • Conversion worksheet • Lunch – extra help time • Displacement and velocity notes • Homework: read p. 137-154 (acceleration and velocity)) • Next class

  3. Calculating Displacement Displacement: Example: Δd = d2 – d1 d1 = initial position d2 = final position Δd = 166 km 20o South of West OR Δd = 166 km 20o [W20o S]

  4. Calculating Total Distance Traveled Because distance is scalar (no direction), simply add together all the distance Example: A student ran 50m east, 20m south, 35m west, and 25m north. The total distance traveled is 230m.

  5. Vectors = magnitude and DIRECTION Therefore, to indicate direction in equations we use negative and positive numbers Direction conventions in Physics:  Right is Positive (+) Left is Negative (-) East is Positive (+) West is Negative (-)  North is Positive (+)South is Negative (-)  Up is Positive (+) Down is Negative (-)

  6. Calculating Total Displacement Total displacement of one object moving several different displacements is the vector sum of the displacements. Δdtotal= d1+ d2 + … Example: A student walks 23m N, turns around and walks 33m S. What is the student’s total displacement?

  7. Calculating Total Displacement Total displacement of one object moving several different displacements is the vector sum of the displacements. Δdtotal= d1+ d2 + … Example: A student walks 23m N, turns around and walks 33m S. What is the student’s total displacement? Δdtotal = d1 + d2 + … = (+23m) + (-33m) = - 10m (or 10m S)

  8. Time (t) • is a point in time as it relates to your reference or zero time. A time interval (t)  is the difference between two times. t = t2 – t1

  9. Speed (v) • A scalar • The distance traveled by an object during a given time interval divided by the time interval V avg = Δd = d2 – d1 Δt t2 – t1

  10. Speed (v) • A scalar • The distance traveled by an object during a given time interval divided by the time interval V avg = Δd = d2 – d1 Δt t2 – t1 Example: A car travelled a distance of 550m in a time interval of 35s. What is its speed?

  11. Velocity (v) • A vector • The displacement of an object during a time interval divided by the time interval V avg = Δd = d2 – d1 Δt t2 – t1

  12. Velocity (v) Example: Two trainers with stopwatches are timing a runner who is training for a race. Both timers start their stopwatches when the runner leaves the starting point. The first trainer is standing at a position that is 12m[S] of the starting point and the second trainer is 65m[S] of the starting point. Each trainer stops her stopwatch when the runner passes her. The first trainer’s stopwatch reads 1.6s and the second trainer’s stopwatch reads 8.7s. What is the athlete’s velocity with running between the trainers?

  13. Using Tables and Graphs... • Graphs are often used to represent the motion of an object. • Graphs are usually draw from the information contained in a data table • A table can be prepared by recording observations of a moving object

  14. Distance vs. Time Once points are plotted on a graph, sketch a line of best fit. Distance(cm) Time (s) • Δd on the y-axis and Δt on the x-axis 60 50 40 30 20 10 0 0 5 10 15 20 25 30

  15. Distance vs. Time Once points are plotted on a graph, sketch a line of best fit. Run 60 50 40 30 20 10 0 Distance (cm) Time (s) • Δd on the y-axis and Δt on the x-axis • The slope of a graph is the rise divided by the run of a line Rise 0 5 10 15 20 25 30

  16. Distance vs. Time 60 50 40 30 20 10 0 Run Distance (cm) • The slope of a graph is the rise divided by the run of a line Slope = Rise = Δd = cm = Speed Run Δt s • The slope of a Distance (cm) vs. Time (s) graph represents the SPEED of an object • The slope of a Displacement (cm [N] or [S]) vs. Time (s) represents the VELOCITYof an object Rise 0 5 10 15 20 25 30

  17. WHAT’S THE VELOCITY?? Displacement (m[E]) Slope = Rise Run = Δd Δt = 60m[E] – 0.0m[E] 7.5s – 0.0s = 60m 7.5s = 8.0 m/s[E] Time (s) Slope = Rise = Δd = cm = Speed Run Δt s 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8

  18. WHAT’S THE VELOCITY?? 60 50 40 30 20 10 0 Displacement (m[E]) 0 1 2 3 4 5 6 7 8 Time (s)

  19. Acceleration  A Vector Quantity • A measure of the change in velocity over a time of period Symbol = a Units = m/s2

  20. Two Ways to Accelerate an Object • Change the speed of the object • Change the direction of an object

  21. Calculating Acceleration a = v = v2 - v1 t t2 - t1 • When an object speeds up, it shows positive acceleration • When an object slows down, it shows negative acceleration

  22. Acceleration Question Example 1) A train starts at rest and reaches a speed of 54km/h in 10 seconds. What is its acceleration?

  23. Acceleration Question Example 2) An object starts from rest and accelerates for a time of 12s. From 5.0 to 8.7 seconds, the car changes speed from 15 m/s to 27.8 m/s. Calculate the acceleration of the object during this time period.

  24. Velocity vs. Time Graph

  25. Velocity vs. Time Graph • The SLOPE of a velocity-time graph gives you the ACCELERATION of the object

  26. Velocity vs. Time Graph • The SLOPE of a velocity-time graph gives you the ACCELERATION of the object • The AREA under the line of a velocity-time graph gives you the DISPLACEMENT of the object

  27. What is the acceleration? Slope = Rise = Δv = m/s= Acceleration Run Δt s ( a )

  28. WORK INDIVIDUALLYFIND THE ACCELERATION? 60 50 40 30 20 10 0 Velocity (m/s[N]) 0 1 2 3 4 5 6 7 8 Time (s)

  29. Graphs and Motion

  30. Graphs and Motion Graphs can be used to show different types of motion. 3 types of graphs that can show the same type of motion:  Distance vs. Time  Velocity vs. Time  Acceleration vs. Time

  31. Type of Motion:An Object or Body at Rest Distance vs. TimeVelocity vs. Time Acceleration vs. Time

  32. Type of Motion:An Object of Body in Uniform Motion Distance vs. TimeVelocity vs. Time Acceleration vs. Time

  33. Type of Motion:An Object or Body in Positive Uniform Motion Distance vs. TimeVelocity vs. Time Acceleration vs. Time

  34. Type of Motion:An Object or Body in Negative Uniform Motion Distance vs. Time Velocity vs. Time Acceleration vs. Time

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