1. Physics Physics is the most basic of the sciences. It is the study of forces, motion, light, heat, sound, energy, matter, atomic and subatomic structure.

2. Kinematics Kinematics is the branch of physics that describes the motion of points, bodies (objects), and systems of bodies (groups of objects) without consideration of the causes of motion.

3. Kinematics Relative motion - All motion is relative. Right now we appear to be motionless relative to each other.

4. Kinematics If an observer from space were to look at us, he would realize that we actually are in motion.

5. Kinematics We are moving because we are on the earth which is rotating.

6. Kinematics The earth is also moving around the sun. The sun is moving through the Milky Way, and so on.

7. Kinematics We appear to be motionless relative to each other, because we are moving together. We say that we are in the same frame of reference.

8. Kinematics In this course we will be talking only about motion of objects relative to the surface of the earth unless otherwise stated.

9. Kinematics Speed is a measure of how fast something is moving. It is measured in terms of a unit of distance divided by a unit of time. Examples are: meters per second miles per hour kilometers per hour The word “per” means “divided by”.

10. Kinematics Instantaneous speed is a speed at any given instant. It is the speed read by the speedometer in your car. Average speed is the total distance covered divided by the time interval required to cover that distance.

11. Kinematics Example: You travel a distance of 100 miles during the time interval of two hours. What is your average speed?

12. Kinematics Notice how the units follow the numbers in the calculations. The units are treated like the letters in algebra.

13. Kinematics In physics speed and velocity mean two different things. Velocity means speed in a given direction. If we say a car is moving at we are talking about speed. Speed is a scalar quantity. It is characterized only by magnitude. If we say a car is moving at north we are talking about velocity. Velocity is a vector quantity. It is characterized by magnitude and direction.

14. Kinematics In order for an object to be moving with constant velocity its speed must be constant, and its direction must also be constant. If either the speed and direction of a moving object is changing, or if both are changing, then it's moving with changing velocity.

15. Kinematics Acceleration Acceleration is defined as change in velocity per time interval

16. Kinematics Acceleration For motion in a straight line

17. Kinematics Acceleration Units for acceleration.

18. Kinematics Acceleration is a vector quantity. It is characterized by both magnitude and direction

19. Kinematics Example: A motorcycle is traveling north at 20 m/s. Two seconds later it's velocity is 40 m/s north. What was its acceleration during the two seconds?

20. Kinematics Solution:

21. Kinematics Distance is a scalar measure of the interval between two locations measured along the actual path connecting them. Displacement is a vector measure of the interval between two locations measured along the shortest path connecting them.

22. Kinematics Example 1: A person is walking east. After walking for a distance of 100 meters, the person reverses direction and walks for a distance of 50 meters west. 1.What was the distance covered? 2.What was the person’s displacement? 3.If the trip took 90 seconds what was the average speed? 4.If the trip took 90 seconds what was the average velocity?

23. Kinematics Example 1: Answer: 1.The total distance was, d=100m+50m=150m 2.If we designate east as the positive direction, than the displacement was, 3.The average speed was 4.The average velocity was

24. Kinematics Example 2: A person is walking east. After walking for a distance of 100 meters, the person reverses direction and walks for a distance of 150 meters west. 1.What was the distance covered? 2.What was the person’s displacement? 3. If the trip took 200seconds what was the average speed? 4.If the trip took 200 seconds what was the average velocity?

25. Kinematics Example 2: Answer: 1.The total distance was, d=100m+150m=250m 2.If we designate east as the positive direction, than the displacement was 1.The average speed was 2.The average velocity was

26. Kinematics Mathematical relationships between distance speed velocity and acceleration. We will use the following symbols: An arrow above a symbol indicates that it is a vector quantity

27. Kinematics The basic relationships assuming that initial

28. Kinematics For a situation where the initial speed or the initial velocity is equal to zero, the following relationships hold.

29. Kinematics When an object is in free fall it means that the only force acting on it is the force of gravity. On earth this means that we must ignore the resistance of air. This is a good approximation if an object has a small surface area, a high density, and is not moving very fast. For example the approximation works well for a dropped steel sphere, but not for a dropped tissue.

30. Kinematics Near the surface of the earth a falling object accelerates downward with a constant acceleration. This acceleration is equal to. Frequently we use a rounded value of for calculations. This acceleration is referred to as acceleration due to gravity and is represented by a lowercase g.

31. Kinematics Free fall

32. Kinematics – free fall Speed versus time table using g=10m/s 2 Elapsed time(seconds)Speed(meters/seco nd) 00 110 220 330 440 550 660 770 880 t

33. Kinematics – free fall Speed versus time table using g=10m/s 2 The slope of this line is the acceleration.

34. Kinematics – free fall Distance versus time table using g=10m/s 2 Elapsed time(seconds)Distance(meters) 00 15 220 345 480 5125 6180 7245 8320 t

35. Kinematics – free fall Distance versus time plot using g=10m/s 2