2. MOTION Motion- An object is in motion when the distance from another object is changing.

3. How can you prove that an object is moving? Reference Point- A place or object used for comparison to determine if something is in motion. An object is in motion if it changes position relative to a reference point. Most common reference point is the Earth

4. How do we measure motion? Speed Velocity Acceleration Momentum

5. What is Motion? Speed The rate of change in position Speed = distance ÷ time or Example: A car travels 300km in 6 hours. What is the speed of the car? = distance time

6. Answer: Speed = distance ÷ time Speed = 300km ÷ 6 hours Speed = 50km/hr

7. More practice 1. How far can a plane travel if it flies 800km/hr for 9 hours? 2. How long does it take a ship to go 500 km if it travels at a speed of 50km/hr?

8. Answer 1. 800km ▪ 9hrs = 7200km hr 2. 500km ÷ 50km = 10 hrs hr

9. What is Motion? Velocity Speed plus direction Example: 50 km/hour north

10. What is the velocity of a boat that travels South from St. Peter to Mankato (10 km) in 15 minutes? – Answer: Speed = distance ÷ time Speed = 10 km ÷ 15 minutes Speed = 0.67 km/min Velocity = 0.67 km/min South

11. Distance-time graphs On your paper, graph the following: – D (m) T (sec) 00 57 57 1014 1521

14. Was your graph a straight line? A distance-time graph which is a straight line indicates constant speed. In constant speed, the object does not speed up or slow down. The acceleration is zero.

15. Graph the following on a distance-time graph: D (m)T (s) 00 51 202 453 804 1255

17. 0 1 2 3 4 5

18. Was your graph a curve? A graph that curves on a distance- time graph shows that the object is accelerating

19. Distance-time graphs Describe the motion of the object as shown in the graph. From 0-8 sec, constant speed: (25 m/sec); From 8-12 sec, no motion; From 12-16 sec, acceleration; From 16-20 sec, constant speed

20. Acceleration by Brainpop 1) What units are used to measure speed? 2) What units are used to measure acceleration? 3) What is another way to say “slowing down” in terms of acceleration?

21. Acceleration The rate of change in velocity Positive acceleration = speeding up Negative acceleration = slowing down (decelerate) Acceleration = V final – V initial Time or = ∆Velocity Time

22. What do the following speed-time graphs depict?

23. Acceleration problem A roller coaster’s velocity at the top of a hill is 10m/s. Two seconds later it reaches the bottom of the hill with a velocity of 26m/s. What is the acceleration of the roller coaster?

24. Answer Acceleration = ∆V/ ∆T a = 26m/s – 10m/s 2 s a = 16m/s 2s a = 8m/s/s or 8m/s 2

25. More acceleration problems 1. A car accelerates at a rate of 20mi/hr/s. How long does it take to reach a speed of 80 mi/hr? 2. A car travels at 60 miles per hour around a curve. Is the car accelerating? 3. A car travels in a straight line at 60mi/hr. Is the car accelerating?

26. Answers: 1. ∆V 80mi/hr a t20mi/hr/s t 4sec = t 2. yes! Because it’s changing direction! 3. no! It’s not changing speed or direction!

27. Deceleration Negative acceleration Example: A car slows from 60mi/hr to 20mi/hr in 4 seconds. What is its acceleration?

28. Answer: Acceleration = ∆V/ ∆T Acceleration = Vf – Vi t a = 20mi/hr – 60mi/hr 4 s a = -40mi/hr 4s a = -10mi/hr/s

29. Momentum Momentum is the tendency of an object in motion to stay in motion Momentum = Mass x Velocity Increase the mass or the velocity to get more momentum.

30. Answer: Momentum of the 300lb player is Momentum of the 300lb player is 300lbs x 5m/s = 1500lb-m/s Momentum of the quarterback is Momentum of the quarterback is 200lbs x 10m/s = 2000lb-m/s 200lbs x 10m/s = 2000lb-m/s The quarterback has a greater momentum! The quarterback has a greater momentum! Which has more momentum: a 300lb football player moving at 5m/s or a 200lb quarterback moving at 10m/s?

31. Momentum problems 2 cars are heading east, car A is traveling 30mi/hr, car B is traveling 60mi/hr. Each car weighs 2000lbs. – What is the momentum of car A? – What is the momentum of car B? – If car B crashes into car A, what is the total momentum?

32. Answers: P=mv P=mv Car A’s momentum = 30mi/hr x 2000lbs Car A’s momentum = 30mi/hr x 2000lbs P A = 60,000 mi-lbs/hr east P A = 60,000 mi-lbs/hr east Car B’s momentum = 60mi/hr x 2000lbs Car B’s momentum = 60mi/hr x 2000lbs P B = 120,000 mi-lbs/hr east Total momentum = P A + P B Total momentum = P A + P B = 60,000 + 120,000 = 60,000 + 120,000 = 180,000 mi-lbs/hr east = 180,000 mi-lbs/hr east