1. Kinematics (Part 2)

2. Position Position = a location with respect to the origin or zero point. Negative and positive values are used to show direction from the origin. Numbers with a direction are a vector quantity.

3. Finding Position 4 miles 6 miles 0 6-4 10 4 0 0 -6-10 Position depends on where you put ‘0’.

4. Distance vs. Displacement Distance: Total length of travel (direction is not considered so distance is a scalar quantity) Displacement: Change in position (direction matters so displacement is a vector quantity) Δd = d f – d i d f : final position ( where you end ) d i : initial position ( where you start ) Can be negative if d f <d i

5. Example 1 4 miles 6 miles 0104 You travel from home to the movies then out to dinner. (A)What is the distance traveled? (B) What is your displacement? (A) Distance = 4 +6 +6 = 16 miles (B)Displacement= d f – d i = 4 - 0 = 4 miles

6. Example 2 4 miles 6 miles 0104 You left the movies, went home, went to dinner, then went to another movie. (A)distance traveled? (B) displacement? (A) Distance =6+4 +4 +6 = 20 miles (B)Displacement= d f – d i = 10 -10 = 0 miles

7. Example 3 4 miles 6 miles 6 -40 You start at home, go to dinner and then go to a movie. (A)distance traveled? (B) displacement? (A) Distance =4+6 = 10 miles (B) Displacement= d f – d i = 6-(-4)= 10 miles

8. Quick Quiz Questions A - C (A)What is the position of your keys? -10 (B)What is the position of your dog? -3 (C)What is the position of the flowers? 0 7 miles 3 miles ? ? 0

9. Quick Quiz Questions D & E 7 miles 3 miles ? ? 0 You pick up your keys, then pick some flowers and give them to your dog. (D)What distance did you travel? 13 miles (E) What is your displacement? -3 – (-10) = +7

10. F. What can be said about the motion displayed in this diagram? It shows the runner is slowing down. Quick Quiz Question F

11. 3 VERY IMPORTANT EQUATIONS… GET YOUR FORMULA CARD Solving Kinematics Problems

12. Average Velocity Vector Quantity Could have a negative value Change in position divided by change in time Δ = delta  “change in” v = Δ d(d f – d i ) “f” = final or end Δ t(t f – t i ) “i” = initial Units are things like (mi/hr, km/hr, m/s)

13. Distance Scalar Quantity Simple manipulation of previous equation Δ D = v x Δ t Units are things like (m, km, mi)

14. Average Acceleration Vector Quantity Change in velocity divided by change in time a = Δ v(v f – v i ) Δ t(t f – t i ) Units are m/s 2

15. USE THE GUESS METHOD Solving Kinematics Problems

16. GUESS Method A systematic way to not only show the correct answer, but also to display your physics knowledge “G” – write down what is given “U” – write down the unknown “E” – write down the equation to be used “S” – substitute values into equation “S” – solve the problem

17. Example Problem #1 How long will it take to travel 50.0 miles in a car traveling at 65 mi/hr? d= 50.0 miles v= 65 mi/hr t=?s Δd = v x t so… t = Δd/v t= (50.0mi)/(65mi/hr) t= 0.77 hr

18. Example Problem #2 A car is traveling at 18.5 m/s. The driver steps on the gas to pass a garbage truck. After 5.0 seconds, the car is traveling at 24.5 m/s. What is the car’s rate of acceleration? v i = 18.5 m/s v f = 24.5 m/s t = 5.0 s a = ??? a = Δv / Δt a = (24.5 m/s – 18.5 m/s) (5.0 sec) a = 1.2 m/s 2