Physics!!!

1. Physics!!! What is it?!?! - “the study of matter, energy, and the interaction between them” http://www.physics.leeds.ac.uk/uploads/tx_templavoila/physics_mphys.png http://www.physics.org/article-questions.asp?id=18 http://images02.olx.gr/ui/17/35/63/1324319948_292723263_1----.png

2. Describing Motion Section 2.1

3. SC Standards Covered • PS-5.1 Explain the relationship among distance, time, direction, and the velocity of an object • PS – 5.2 Use the formula v=d/t to solve problems related to average speed or velocity • PS – 5.6 Represent linear motion of objects on distance – time graphs

4. Motion • Motion – when an object changes its position • Reference point- an indicator that orients you---the place from which you measure, record, or witness an event • Distance – how far an object has moved -measured in meters (m) • Displacement – distance and direction of an objects change of position from a starting point (see pg. 38-39 in text)

5. Displacement Distance = 50m + 30m = 80 m Displacement = 20m North of starting line

6. Ben walks 4 meters East, 2 meters South, 3 meters West, and finally 2 meter North. • Distance = 11m • Displacement = 1m East • What is the displacement of the cross-country team if they begin at the school, run 10 miles and finish back at the school? • Distance = 10 miles • Displacement = 0 miles

7. Pythagorean Theorem • Displacement: • a2 + b2 = c2 • Example: Joe walks 4m North turns and walks 3m west. What is Joe’s distance and displacement?

8. You try! Sarah wants to ride her bike to visit her friend down the road. She rides 2 miles south, turns and rides 3 miles east. She turns again and rides 1 mile north. What is Sarah’s distance and displacement?

9. Calculating Speed • Speed – the distance an object travels per unit time Speed = distance = d time t • Units will always be some distance measurement divided by some time measurement

10. Types of Speeds • Average speed– total distance traveled divided by total time traveled • Instantaneous speed– speed at a given point in time. • This is what is shown on a speedometer http://www.toptenz.net/wp-content/uploads/2014/01/radar-gun.jpg

11. Calculating Speed Practice Example #1 Suppose you ran 2 km in 10 min. What is your speed? s = d t = 2 km 10 min. = 0.2km/min.

12. Example #2 Sound travels at 330 m/s. If a lightning bolt strikes the ground 2 km away from you, how long will it take for the sound to reach you? 2km = 2000 m s = d t 330 m/s = 2000m t (330)(t) = 2000 (330)(t) = 2000 330 330 t = 6.06 s

13. You Try  • A passenger elevator travels from the first floor to the 60th floor, a distance of 210 m, in 35 s. What is the elevator’s speed? • A motorcycle is moving at a constant speed of 40 km/hr. How long does it take the motorcycle to travel a distance of 10 km? • How far does a car travel in 0.75 hr if it is moving at a constant speed of 88 km/hr?

14. Velocity • Velocity– speed of an object and the direction of its motion • Speed can remain constant but if the direction of the object changes its velocity is changing -Calculated the same as speed v= d t

15. Vector vs. Scalar • Scalar- magnitude only • Example: distance or speed • Vector- magnitude and direction • Example: displacement or velocity

16. Scalar or Vector ? a. 5 m b. 30 m/sec, East c. 5 mi., North d. 20 degrees Celsius e. 256 bytes f. 4000 Calories

17. Graphing Motion • Graph distance on the y-axis and time on the x-axis Slope = rise = distance = speed run time Slope = (y2-y1)/(x2-x1)

18. A … Starts at home (origin) and goes forward slowly B … Not moving (position remains constant as time progresses) C … Turns around and goes in the other direction quickly, passing up home

19. Your turn! Suppose a bus is traveling along a highway. It travels 100 km in the first 2 hrs and 120 km in the second 2 hrs. It stops for one hour, then it finishes the trip by going 100 km in two hours. Draw a distance verses time graph of the bus’s motion.