1. Mechanics - Kinematics
Define:
Displacement – distance & direction from reference point Dx , Dy, Dz.
Pos or neg sign gives direction.
Velocity – rate & direction object changes in position Dx /t or s/t.
sign follows displacement.
Acceleration – rate change of velocity Dv /t.
Sign give change in vel – not direction.

2. Velocity Average velocity = s tot/ t tot.
Instantaneous vel is a limit.
Can find from slope of tangent to point.

3. Ex 1: A bus travels north 180 km in 2. 2 hours
Ex 1: A bus travels north 180 km in 2.2 hours. It stops for 30 minutes turns and drives 60 km south in 45 min. What is its average velocity in km/h.
vav = stot / t tot.
34.8 km/h.

4. Kinematics Equations IB Tables pg 6
Uniform/constant acceleration: Dv same increment.
u = vi
v = vf
s = displ.
a = Dv/t

5. Acceleration of gravity g remarks.
Constant/uniform m/s2 on Earth.
Negative sign is arbitrary!
Often use 10 m/s2 as estimate.
Air resistance in atmosphere causes objects to reach terminal fall velocity after falling for a time.
Wind/Air resistance increases with speed. Fuel efficiency in cars better at slower speeds.

6. Relative Motion
Ex 2:
You are standing on a railway platform. A is train moving at 25 m/s to the right. On it is a passenger walking to the right at 2 m/s. What is his velocity relative to you?
27 m/s.
If the velocity of object A, relative to a fixed point is VA, the velocity of object B, relative to the same fixed point is VB, then the velocity of A relative to B is the vector difference: is VA - VB.

7. Ex 3:
Car A is traveling 15 m/s and is overtaken by car B which is moving in the same direction at 18 m/s. What is the velocity of car B relative to car A?
Vb – Va =
3 m/s.
What is the velocity of Car A relative to Car B?
Va – Vb - 3 m/s

8. Ex 4: A boat heads north across a river 90 m wide
Ex 4: A boat heads north across a river 90 m wide. The speed of the boat relative to the shore is 1.8 m/s but the river pushes the boat east at 1.2 m/s. A) What is the speed of the boat relative to the water? B) How far will it land downstream when it arrives at the opposite shore?
2.2 m/s
60-m.

9. Practice Sheet “IB Kinematics Questions”

10. IB Motion Graph Review

11. Distance/Position/Displacement Time Graphs Constant vel.
Starting
point
Slope = Velocity
Slower Velocity

12. Positive Negative Quadrants Where object is w/ref to starting point.

13. What is the object’s:
a. displacement
distance 10 30

14. Constant Velocity/Speed

15. Constant / Uniform Acceleration. On velocity time graph accl
Constant / Uniform Acceleration. On velocity time graph accl. is slope of straight line.
+ or neg a shown?

16. What’s going on here physically?

17. Sign of velocity is direction of motion shown by the quadrant.
What does this show?

18. What does -v mean?

19. What does the sign of slope mean?

20. Displacement = Area Under Curve v = d/t then, vt = d.

21. To find displacement, calc area of triangle + rectangle.

22. When is object back at start point?
+ area must = - area

23. Acceleration – time graphs
Graph d-t, v-t, a-t tossed ball & caught at same height.

25. In Class. Kerr pg 39 Ex 2.1 #1 Hwk Kerr pg 71 Topic 2.1 #1-4.