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Physics 10

Physics 10. Unit 1 Newton’s 1 st Law Unit 2 Newton’s 2 nd Law Unit 3 Electricity Unit 4 Waves Unit 5 Astrophysics. Newton’s 1 st Law. An object moving with a constant velocity will continue to move with a constant velocity unless acted on by an unbalanced force.

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Physics 10

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  1. Physics 10 Unit 1 Newton’s 1st Law Unit 2 Newton’s 2nd Law Unit 3 Electricity Unit 4 Waves Unit 5 Astrophysics

  2. Newton’s 1st Law An object moving with a constant velocity will continue to move with a constant velocity unless acted on by an unbalanced force. An object at rest will remain at rest unless acted on by an unbalanced force. This is often called the “law of inertia”.

  3. Scalars and Vectors • Scalars have magnitude and no direction • Vectors have magnitude and direction (draw arrows!)

  4. Scalars and Vectors Which of the pictures are scalars and which are vectors?

  5. Displacement • Distance has no direction • Displacement is measured from a reference point

  6. Displacement To calculate the displacement of an object Δd = dfinal – dinitial Δ = “change in”

  7. Example 1: A truck is driving east and passes a mark on the road that says 300 meters, and then passes another one 10 seconds later that says 450m. Determine the distance the truck moved. What would be its displacement?

  8. Example 2: You start walking home from school. After walking 1.3km North, you get a phone call from your mom asking if you can meet her at the mall. You will have to turn around and walk 2.5km south. Determine your distance and displacement to get to the mall.

  9. Displacement Displacement = Distance =

  10. Velocity Velocity is the rate of change of position. Velocity is a vector(speed and direction) We often use the word speed but it is a scalar and does not have direction. We will try to use velocity instead.

  11. Example 3: What speed did you drive on Sheik Zayed today? What velocity did you drive on Sheik Zayed today?

  12. Average Velocity v = velocity (ms-1) sometimes we write it as m/s, meters per second d = displacement (m) t = time (s) Total Displacement Total Time

  13. Average Velocity If we drove 150km to Abu Dhabi in 2 hours we can use those values to determine our average velocity.Why can’t we just look at the speedometer and use that velocity? The important question is, “how far did we travel and how long did it take”?

  14. Example 5: A car drives along the highway at 115km/h for 2.50 hours. Once in the city, the car drives at 60.0 km/h for the next 0.500 hours. Determine the average velocity of the car.

  15. Positives and Negatives The value of our vectors need to have a direction applied to them in order for us to do calculations with them.

  16. Positives and Negatives These positive and negative values are what define the vectors so they are very important!!!

  17. Example 6: A train is moving backwards at a velocity of 13.5 km/h for 6.40 minutes. Determine the train’s displacement.

  18. Example 7: Look back at Example 2. Determine your speed and velocity if the walk took you 1 hour and 10 minutes.

  19. Displacement – Time Graphs Let’s look at the pieces of a displacement – time graph.

  20. Displacement – Time Graphs 0 to 90 seconds • Straight line slope means constant positive velocity (not speeding up or slowing down) • Slope the graph (rise/run) always equals the velocity (displacement/time)

  21. Displacement – Time Graphs 90 seconds to 150 seconds • Out of breath! • Position is not changing but time is still passing…you’re standing still! • A slope of zero means a velocity of zero!

  22. Displacement – Time Graphs 150 seconds to 240 seconds • Straight line slope means constant positive velocity again • Steeper slope means faster velocity than before!

  23. Displacement – Time Graphs 240 seconds to 300 seconds • A downward slope shows your displacement is decreasing. You must be running backwards! • A negative slope means a negative velocity • Since velocity is a vector the negative just means you are going in the opposite direction as before

  24. Displacement – Time Graphs 300 seconds to 360 seconds • Out of breath again…stopped!

  25. Displacement – Time Graphs 360 seconds to 500 seconds • Your displacement is increasing again but there is a curve in the graph now. What does this mean? • Is the velocity constant in this section

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