1. MOTION An Introduction

2. Thoughts about Motion: A Short History

3. Aristotle Greek philosopher (384-322 BCE)

4. Assumptions: 1.Natural laws could be understood by logical reasoning 2.Heavy objects fall faster than light objects 3.Moving objects must have forces exerted on them to keep them moving

5. Galileo Galilei Italian (1564-1642)

6. Assumptions: 1. Natural laws could be understood by experimentation 2. Objects of different weights fall at the same rate (except air resistance)

7. Leaning Tower of Pisa

8. Assumptions (continued) 3. Moving things, once moving, continue in motion without the application of forces (ignoring friction)

9. Sir Issac Newton English (1642 -1727)

10. Sir Issac Newton

11. Assumption: Newton’s First Law : Inertia Every object remains at rest or in motion (unless acted upon by an outside force)

12. Motion : Speed 1. = how fast an object is moving 2. speed = distance / time Units = mi/hr, km/s, m/s, ft/sec, cm/s, in/s

13. Motion : Speed Average speed = total distance covered time interval

14. Speed examples 1.It took me 12.8 hours to drive to Vegas. (914 miles) What was my average speed?

15. Speed Example 1 Av speed = total distance covered time interval

16. Speed Example 1 = 914 mi = 71.4 mi / hr 12.8 hr

17. Speed example 2 2. If I drive at an average speed of 79 mph ( mi / hr), how many miles can I cover in 4.5 hours?

18. Speed example 2 total distance = (av. speed) (time) = (79 mi ) (4.5 hr) = (hr) 355.5 miles

19. Speed example 3 3. How long will it take to drive to Chicago (1000 miles) if your average speed is 63 mi/hr?

20. Speed example 3 Time = distance = av. speed

21. Speed example 3 (1000 mi) = (63 mi/hr)

22. Speed example 3 15.9 hrs.

23. SPEED IS RELATIVE Everything is moving Earth is rotating (spinning) Earth is orbiting around the sun Galaxy is expanding

24. SPEED IS RELATIVE Motion is measured relative to something 1. e.g. Train relative to track 2. Space shuttle relative to Earth 3. Other examples?

25. SPEED IS RELATIVE How fast is the Earth is moving?

26. SPEED IS RELATIVE 30 km/sec Relative to the sun So… you are moving 30 km/sec The desk is moving 30 km/sec

27. VELOCITY = speed plus a DIRECTION of motion v = distance time

28. VELOCITY Problem Two cars are driving in opposite directions. Car 1 is going 60 mi/hr. Car 2 is also going 60 mi/hr. Do both cars have the same speed?

29. VELOCITY Problem 1 Yes Do both cars have the same velocity? Why or why not?

30. VELOCITY Problem No. Because they are not traveling in the same direction. They have the same speeds, but opposite velocities.

31. Acceleration

32. = (change in velocity) (change in time) = ∆v/ ∆ t = v 2 – v 1 t 2 – t 1

33. Acceleration NOTE : Deceleration = negative acceleration So, stepping on the brake = − acceleration

34. Acceleration Problem 1 A 1965 T-bird with a 390 cubic inch engine can go from rest to 60 mi/hr in 8 seconds. What is its acceleration in m/sec 2 ?

35. Acceleration Problem 1 What formula to use? How about the acceleration formula?

36. Acceleration Problem 1 Acceleration = ∆v/ ∆ t = v 2 – v 1 t 2 – t 1 Right, but we need m/sec, not mi / hr, what to do?

37. Acceleration Problem 1 SO, we need to convert…. (6x10 1 mi) (1km) (10 3 m) (1 hr) (hr) (6.2x 10-1 mi) (1 km) (3.6x10 3 s) = 6 x 10 4 m = 2.6 x 10 2 m / s 2.23x 10 2 s

38. Acceleration Problem 1 But, we need to know m/ s 2 (2.6 x 10 2 m/s)= 32.5 m/s 2 (8 s)