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Physical Science

Physical Science. Motion. What is motion? Do all objects fall at the same rate? Why do apples fall to earth? Why doesn’t the moon fall to earth?. How is distance different from displacement? Can they be the same? Explain. Distance and Displacement. Are You Moving ?.

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Physical Science

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  1. Physical Science Motion

  2. What is motion? • Do all objects fall at the same rate? • Why do apples fall to earth? • Why doesn’t the moon fall to earth?

  3. How is distance different from displacement? • Can they be the same? Explain.

  4. Distance and Displacement

  5. Are You Moving ? • You are sitting down, reading a book…. • Are you moving?

  6. An object is in motion when its distance from another object is changing. Motion Definition

  7. Relative Motion • Relative motion is movement in relation to a REFERENCE POINT. • This is called Frame of Reference. • Motion depends on the “Frame of Reference” • Therefore an object is in motion if it changes position relative to a reference point.

  8. Frame of Reference Example Look at the figures. In fig.1, the car is to the right of the tree. In fig.2, after 2 seconds, the car is to the left of the tree. As the tree does not move, the car must have moved from one place to another. Therefore, here the tree is considered as the frame of reference

  9. Distance vs. Displacement • Distance is the length of a path between two points. • SI unit? • Meters!! • Displacement is the direction from the starting point and the length of a straight line from the starting point to the ending point. • Sometimes it is the same as distance, but many times it is not.

  10. Distance vs. Displacement Animation • http://www.tutorvista.com/content/physics/physics-i/motion/difference-distance-displacement.php • Another example! • http://www.youtube.com/watch?v=Q9D0Yleyflc (Tutorial)

  11. Scalar Quantities • Show magnitude only (magnitude can be size, length, or amount) • Examples: Speed, time, temperature, distance

  12. Vector Quantities • Show magnitude and direction • Velocity, acceleration, force, displacement • May be graphically represented • Arrows • Despicable Me – Vector video clip

  13. Vectors • Vectors are a method used to visually show forces • A vector is a quantity which has both magnitude (size) and direction. • The length of the arrow shows the magnitude of the vector. • The angle of the arrow shows the vector's direction. • Just like numbers, we can add two or more vectors together and get a net force called the resultant

  14. Adding 2 or More Vectors Fig 1 Fig 3 Fig 2 Add vectors A and B to get the Resultant C A + B = C Fig 1 - shows the magnitude & direction of the 2 vectors we are adding Fig 2 – we move the beginning of vector B to the end of Vector A, making sure to keep the magnitude & direction exactly the same Fig 3 – Connect the beginning of Vector A to the end of Vector B, this is your “Resultant” C.

  15. Combining Displacements • You can add vectors using “vector addition” • When two displacements have the same direction, you can add their magnitudes. • If two displacements are in opposite directions, the magnitudes subtract from each other.

  16. Displacement along a Straight Line

  17. Displacement that isn’t along a straight path Suppose a person moves 3 meters from A to B and 4 meters from B to C as shown in the figure. The total distance traveled by him is 7 meters. But is he actually 7 meters from his initial position? No, he is only 5 meters away from his initial position i.e., he is displaced only by 5 m, which is the shortest distance between his initial position and final position. Use Pythagorean’s Theorem! a2 + b2 = c2

  18. Distance vs. Displacement Problems • http://www.tutorvista.com/content/physics/physics-i/motion/distance-and-displacement-animation.php

  19. Distance vs. Displacement • David walks 3 km north, then turns and walks 4 km east. • Amy runs 2 miles south, then turns around and runs 3 miles north. • Jermaine runs exactly 2 laps around a 400 meter track. • Derrick crawls 4 feet then turns 90 degrees and crawls 6 feet. • Ray runs 30 feet north, 30 feet west, and then 30 feet south. • Jamison turns around 5 times. • Cassidee walks 1 mile then turns 90 degrees and walks 2 miles. • Taja walks two miles from her door to the park, then returns home to her door.

  20. Distance vs. Displacement continued • Sandy ran 3 blocks north, and then 2 blocks west. • Neva swam 3 complete laps in a 50 meter pool. ( 1 lap is to the other side and back) • John flies at a heading of 90 degrees for 20 km, turns to 270 degrees and flies for another 10 km before crashing into a flock of geese. • Cameron flies at a heading of 180 degrees for 13 km, turns to 90 degrees and flies for another 30 km before crashing into the Alico building. • Marissa flies at a heading of 270 degrees for 5 km, turns to 90 degrees and flies for another 10 km before crashing into Alex • Alex flies at a heading of 0 degrees for 3 km, turns to 270 degrees and flies for another 4 km before crashing into Marissa • Taylor flies at a heading of 90 degrees for 20 km, turns to 180 degrees and flies for another 25 km before crashing into a Bob Marley billboard.

  21. Example problems • What is the total distance of a person who over the course of a week ran a 5Km, 10Km, and biked a 150Km? • Julia drove 2.56x105 m S to school today, and then drove 1.42x103 m N to Samantha’s house after school. What was her total displacement?

  22. More Examples • Chris drove 1300m W to Logan’s house then they drove 2500m S to meet Brittany and Whitney at Whitney’s house. From there they all drove 3800m E to watch the JV Football game, what was Chris’ total displacement?

  23. Speed!! • Begins here!!

  24. Distance-Time Graphs The distance traveled by an object in a period of time often is expressed using a line graph. A line graph visually conveys information using sets of data points. 1. Copy the blank graph below on your paper. Complete the graph by plotting the given data points on the graph. Each set of data points represents (time, distance). Note that time is measured in seconds and distance is measured in meters. Connect the plotted points with a straight line. Data points: (0, 0), (2, 40), (4, 80), (6, 120), (8, 160), (10, 200) 2. Describe the motion shown on the graph 200

  25. the object is traveling at a constant speed and/or that the object traveled 200 meters in 10 seconds

  26. Speed • Comparison of time and distance • A scalar quantity (what does this mean?) • [magnitude only] • Distance units include: inches (in), feet (ft), miles (mi),meters (m), kilometers (km), centimeters (cm), light year, etc. • Time units include minutes (min), seconds (sec), hours (hr), years (yr), etc. • Speed can be any distance unit divided by any time unit!! • Mi/hr, ft/sec, km/min • Distance traveled per unit time • S = d / t (speed = distance/time) • T = d / s • D = s x t • What is the speed of a car that traveled 75 km in 1.5 hr? S = D / T = 75km / 1.5 hr = 50 km/hr

  27. Please get out your Distance/Displacement worksheet and your Speed Problems worksheet!

  28. Speed • Measured in m/s • If you travel 2m in 1 sec, what is your speed? • If you travel 15m in 12 sec, what is your speed? • Car traveling at 80km/hr. What is this speed in m/s? • 80 km x 1 hr x 1000m = 22.2 m/s hr 3600 sec 1 km

  29. If the Algebra Stumps you!! • V = d / t • T = d / v • D = v x t Divide here! Multiply here!

  30. Speed Worksheet – p.1

  31. Velocity is speed with a direction • Speed AND direction • A vector quantity [magnitude & direction] • Written like: 125 miles/hour east or 83 m/sec towards the house • What is the velocity of a jet that traveled 1623 mi North in 83 min? • V = D / T • =1623 mi / 83 min • =19.5 mi/min North • You can add velocities just like you did displacements, with vector diagrams

  32. Some Conversion formulas you may need: Write these in your notes!!!!! • 1 mile = 1.609 km • 1 km = .62 miles • 1 mile = 5,280 feet • 1 mile = 1,760 yards

  33. Average speed - computed for the entire duration of a trip • Instantaneous speed - measured at a particular instant, like when you check your speedometer

  34. ppe

  35. Average Speed • Avg speed = total distance / total time V = d / t • If a object moves at 104 km/hr for 12 hours, what distance has it traveled? • If an object moves 640 km in 11 hours, what is its speed? • If a car moves at an average speed of 60 mi/hr for 24 hours, what distance has it traveled? What is this distance in kilometers? • (1 mile = 1.609 km)

  36. Average Speed vs. Average Velocity • Avg speed = total distance / total time V = D / t • Avg velocity = total displacement / total time V = D / t

  37. The slope of a line on a distance-time graph is speed

  38. Average Speed(Average Velocity) What is the average speed after two minutes? What is the average speed between 2 and 4 minutes? What is the average speed for the entire trip? Answers on next slide!! Let’s see how you did!!

  39. Answers for Average Speed or Average Velocity What is the average speed after 2 minutes? total distance is 75m, total time is 2 minutes. S = D/T S = 75m / 2min S= 37.5 m/min What is the average speed between 2 & 4 minutes? total distance: 110m – 75m = 35m total time: 4min – 2min = 2minutes total time S = D/T S = 35m / 2min S= 17.5 m/min Average speed = total distance / total time

  40. SpeedConstant Speed • Speed that does not change • Instantaneous speed that does not change

  41. Velocity Video Clip • C:\Movies\Physical Science\Motion\phy03_vid_velocity\phy03_vid_velocity_300.mov • This is on my hard drive at school…if you are looking at this on my website, click the link below and view the video • http://www.teachersdomain.org/resource/phy03.sci.phys.mfw.velocity/

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