1. Physics 11 Mr. Jean February 7 th, 2012

2. The plan: Video clip of the day HW Check Lab contracts Textbooks Position and movement Review of last day Constant acceleration equations

3. Homework Check: Re-arranging formula’s sheet. –Algebra –Scientific Notation

4. Lab Safety Contracts: Most people have passed this in however; if you have lost your copy there is a link on my webpage for you to print out. Also note: I’ve changed my website some to better accommodate cell phones. Let me know if this has helped.

5. Textbooks: How many people have their physics textbooks? If you do not have it get it soon!

6. Review of last day: Kinematics That branch of physics which deals with the motion of objects without reference to the forces which act on the system

7. x i = starting location “initial position” (m) x f = ending location “final position” (m) v f = final velocity (m/s) v i = initial velocity (m/s) a = acceleration (m/s 2 ) θ = angle in degrees t = time (s) Important Variables:

8. Vectors & Scalars: Scalars are quantities we measure in everyday life. (Mass, time, energy etc…) In physics we normally describe motion in terms of vector. We have a quantity, but also a direction the quantity is travelling in. Distance and speed are scalars; however positive displacement, velocity, and acceleration are vectors.

9. Scalars vs. Vectors: Scalar QuantitiesVector Quantities Distance – 15kmDisplacement – 15km [N45 0 E] Speed – 30 m/sVelocity – 30m/s [S]

10. The basics of measuring motion: Speed is measured in meters per second (m/s) x i = starting location (meters) x f = final location (meters) t i = starting time (seconds) t f = end time (seconds) Speed: Speed = x f – x i t f - t i

11. The basics of measuring motion: Average Speed: Average Speed = Total distance (m) Total time (s) –Always measured in meters per second (m/s) for physics class.

12. The basics of measuring motion: Velocity is a vector, thus you must give it a direction. The international SI unit for velocity is meters per second (m/s). x i = starting location (meters) x f = final location (meters) t i = starting time (seconds) t f = end time (seconds) Velocity: v = x f – x i t f - t i

13. The basics of measuring motion: a = acceleration (m/s 2 ) v i = initial velocity (m/s) v f = final velocity (m/s) t i = Starting time (s) t f = End time (s) Acceleration: Acceleration [Direction] = v f – v i t f - t i

14. Constant Acceleration: v f = v i + at v f = Final velocity in m/s v i = Initial velocity in m/s a = acceleration in m/s 2 t = time in seconds

15. Example #1 A slip and slide uses gravity to accelerate people down a hill. On Ron’s awesome slip and slide people accelerate from 0m/s to 20m/s in 4 seconds. Find the acceleration in this situation.

16. Ron’s Slip and Slide What is Ron’s slip and Slide?

17. Example #2: Hailey’s ball is rolling away from her at 2m/s. It start to accelerate down a steep hill at the rate of 4m/s 2 and continues to do so for 4 seconds. What is the balls final velocity?

18. Position & Distance: We need a “starting point”! This lets us describe the position in terms of fixed/pre-determined point. –Normally we make a reference point of (0, 0). –The position of an object is the separation between that object and a reference point. –We use +, - to describe it’s relative position.

19. Position:

22. CBR – Motion detectors: Have you used the Ti-83 ranger motion detectors before? We are headed to the lab on Friday.

23. Constant Acceleration Equations: Let’s get back to some situational questions involving constant acceleration.

24. x f - x i = v i t + ½ (a) (t 2 ) x f = Final distance (m) x i = Initial distance (m) v i = Initial velocity (m/s) t = time (s) a = acceleration (m/s 2 ) ∆d = change in distance (m) Constant Acceleration:

25. Example: x f - x i = v i t + ½ (a) (t 2 ) Starting from rest at the start line Brandon roller blades westwards with a constant acceleration of 2m/s 2 for 15 minutes. What is his final distance?

26. Example: x f - x i = v i t + ½ (a) (t 2 ) What is his final distance?

27. Example: x f - x i = v i t + ½ (a) (t 2 ) Over the distance of 4000m Jessica’s car accelerates at the rate of 30m/s 2 [E] with for 15 seconds. What is Jessica’s initial velocity?

29. To do: Text book readings –Read pages –p. 41 – 45 –p. 47 – 49 –p. 51 – 52 –p. 61 – 64 –Thursday we are in the lab.