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# C2 motion

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### C2 motion

1. 1. Chapter 2 Motion2-1. Speed 2-8. Mass2-2. Vectors 2-9. Second Law of Motion2-3. Acceleration 2-10. Mass and Weight2-4. Distance, Time, and 2-11. Third Law of Motion Acceleration 2-12. Circular Motion2-5. Free Fall System 2-13. Newtons Law of2-6. Air Resistance Gravity2-7. First Law of Motion 2-14. Artificial Satellites
2. 2. 2-1. Speed• Definitions: – Speed • The rate at which something moves a given distance. • Faster speeds = greater distances – General formula for speed: • Speed = distance / time • Abbreviations commonly used: d = distance t = time v = speed v = d/t
3. 3. 2-1. Speed Velocity d 100m iles m iles v 40 40m ph t 2.5hours hour Distance d v t 30 miles 6hours 180miles hour Time d 100m iles m ilest 2.5 2.5hours v 40m iles/ hour m iles/ hour
4. 4. 2-1. SpeedAverage speed is the total distance traveled by an object divided by the time taken to travel that distance.Instantaneous speed is an objects speed at a given instant of time.
5. 5. 2-2. VectorsMagnitude of a quantitytells how large thequantity is.Scalar quantities havemagnitude only.Vector quantities haveboth magnitude anddirection.
6. 6. 2-2. VectorsVelocity is a vector quantity that includes both speed anddirection.
7. 7. 2-3. AccelerationAcceleration of an object is the rate of change of itsvelocity and is a vector quantity. For straight-line motion,average acceleration is the rate of change of speed: change in speed vf viAccelerati on a time interval t
8. 8. 2-3. Acceleration 3 Types of Acceleartion Speeding UpSlowing Down Turning
9. 9. 2- 4. Distance, Time and Acceleration (V1 + V2) (20mph + 60mph)Vavg = = 40mph 2 2 d = vavg t 30mph 2hr = 60miles d = ½at2 ½ 10m/s/s 52 = 125m
10. 10. 2-5. Free FallThe acceleration ofgravity (g) for objectsin free fall at theearths surface is 9.8m/s2.Galileo found that allthings fall at the samerate.
11. 11. 2-5. Free FallThe rate of fallingincreases by 9.8 m/severy second. Height = ½ gt2 For example: ½ (9.8 )12 = 4.9 m ½(9.8)22 = 19.6 m ½ (9.8)32 = 44.1 m ½ (9.8)42 = 78.4 m
12. 12. 2-5. Free Fall A ball thrown horizontally will fall at the same rate as a ball dropped directly.
13. 13. 2-5. Free Fall A ball thrown into theair will slow down, stop, and then begin to fall with the accelerationdue to gravity. When it passes the thrower, it will be traveling at the same rate at which it was thrown.
14. 14. 2-5. Free FallAn object thrown upward at an angle tothe ground follows a curved path called a parabola.
15. 15. 2-6. Air Resistance• In air… – A stone falls faster than a feather • Air resistance affects stone less• In a vacuum – A stone and a feather will fall at the same speed.
16. 16. 2-6. Air Resistance• Free Fall – A person in free fall reaches a terminal velocity of around 54 m/s – With a parachute, terminal velocity is only 6.3 m/s • Allows a safe landing
17. 17. 2-6. Air Resistance• Ideal angle for a projectile – In a vacuum, maximum distance is at an angle of 45o – With air resistance (real world), angle is less • Baseball will go furthest hit at an angle of around 40o
18. 18. 2-7. First Law of MotionThe first law ofmotion states: Ifno net force actson it, an object atrest remains atrest and an objectin motion remainsin motion at aconstant velocity.
19. 19. Foucault PendulumInertia keeps a pendulumswinging in the samedirection regardless of themotion of the earth. Thiscan be used to measure themotion of the earth. As theFoucault Pendulum swingsit appears to be rotating,but it is the earth that isrotating under it. To theright is the FoucaultPendulum at the Pantheonin Paris, France.
21. 21. 2-8. MassInertia is the apparent resistancean object offers to any change inits state of rest or motion.
22. 22. 2-9. Second Law of Motion Newtons second law of motion states: The net force on an object equals the product of the mass and the acceleration of the object. The direction of the force is the same as that of the acceleration. F = Ma
23. 23. 2-9. Second Law of MotionA force is anyinfluence thatcan cause anobject to beaccelerated.The pound (lb) is the unit of force in the British system of measurement:1 lb = 4.45 N (1 N 2 1 newton 1 N 1 (kg)(m/s ) = 0.225 lb)
24. 24. 2-10. Mass and Weight• Weight Definition: The force with which an object is attracted by the earth’s gravitational pull • Example: A person weighing 160 lbs is being pulled towards the earth with a force of 160 lbs (712 N). – Near the earth’s surface, weight and mass are essentially the same Weight (mass)(acc elerationof gravity) w mg
25. 25. 2-11. Third Law of MotionThe third law of motion states: When one object exerts a force on a second object, the second object exerts an equal force in the opposite direction on the first object.
26. 26. 2-11. Third Law of Motion Examples of the 3rd Law
27. 27. 2-12. Circular MotionCentripetal force is the inward force exerted on an objectto keep it moving in a curved path.Centrifugal force is the outward force exerted on theobject that makes it want to fly off into space.
28. 28. 2-12. Circular Motion
29. 29. 2-12. Circular Motion 833 N is needed to make this turn.If he goes too fast, which wheels are likely to come off the ground first?
30. 30. 2-13. Newtons Law of Gravity Gm1m2 Gravitatio nal force F 2 RG = 6.67 x 10-11N•m/kg2
31. 31. 2-13. Newtons Law of Gravity• How can we determine the mass of the earth using an apple? – This illustrates the way scientists can use indirect methods to perform seemingly “impossible tasks”
32. 32. 2-13. Newtons Law of Gravity• How can we determine the mass of the earth using an apple? – This illustrates the way scientists can use indirect methods to perform seemingly “impossible tasks” GmM = mg Gravitational force on apple F R2 gR 2 (9.8m / s 2 )(6.4 106 m) 2 M 6 1024 kg G 6.67 10 11 N m2 / kg 2
33. 33. 2-15. Artificial Satellites• The worlds first artificial satellite was Sputnik I, launched in 1957 by the Soviet Union. GPS-Global Positioning Satellite
34. 34. 2-15. Artificial SatellitesThe escape speed is the speed required by an object to leave the gravitational influence of an astronomical body; for earth this speed is about 40,000 km/h.
35. 35. 2-15. Artificial SatellitesThe escape speed is the speed required by an object to leave the gravitational influence of an astronomical body; for earth this speed is about 40,000 km/h.