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# Physics study guide

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DR V's Traditional Physics. You're welcome :)

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### Physics study guide

1. 1. <ul><li>Distance – Length from one point to another; always +.
2. 2. Displacement - The length of the straight line drawn from its initial position to the object’s final position; can be + or -.
3. 3. Change in position = final – initial position or (∆X = Xf – Xi)
4. 4. Speed – Measure of the distance over time. Has no direction, only magnitude.
5. 5. Average speed = distance traveled/time of travel.
6. 6. Velocity – Displacement divided by the time interval. Describes a motion with both a direction and numerical value (magnitude).
7. 7. Average Velocity = (∆X / ∆T) or displacement/time interval.
8. 8. Cannot use the average velocity equation (v=∆x / ∆t) when there is acceleration. You have to use (change in velocity / time required for change).
9. 9. Yes, but only if the final displacement is zero.
10. 10. Constant speed, but the velocity is changing due to its direction.
11. 11. Typical metric units of displacement – meters.
12. 12. Slope of a v-t graph is the acceleration and never curves. The area (under the slope) is the displacement.
13. 13. Slope of a d-t graph is the velocity. Curved line = acceleration. The area (under the slope) is the velocity.
14. 14. Area of an a-t graph is the change in velocity.
15. 15. Horizontal line on a d-t graph means that the displacement is currently 0 (no movement). On a v-t graph – it is a constant velocity. On an a-t graph – there is no acceleration (constant velocity).
16. 16. Negative slope on a d-t graph means that it has a constant negative velocity. On a v-t graph, the acceleration is negative.
17. 17. Beneath the axis on a v-t graph – object is slowing down.
18. 18. Three ways of acceleration: increasing speed, decreasing speed, and changing direction.
19. 19. Turn a corner with constant acceleration? No, because the velocity changes due to direction. Zero acceleration? No, because the speed would also be zero.
20. 20. Negative velocity and positive acceleration? Yes, with free-falling objects. Positive velocity and negative acceleration? Yes, with projectiles.
21. 21. Acceleration of an object in freefall – 9.8 m/s/s. What are some examples? Baseball, football, etc.
22. 22. Acceleration – Zero in horizontal. -9.8 m/s^2 in vertical. At peak, horizontal is 0, vertical is 0. Just before caught, the acceleration is force of gravity.
23. 23. Vertical velocity of ball thrown straight up when it reaches its peak = 0 m/s.
24. 24. Velocity upward – 20 m/s. Speed before caught – 9.8 m/s.
25. 25. Displacement – 0.5(initial velocity+final velocity)(time interval)
26. 26. 0.5(0+9.8)(1) = 1.96 m. Or TNEOMS equation, Dx=(0)(1)+0.5(9.8)(1)^2 =1.96 m.
27. 27. What angle to travel farthest – 45 degrees.
28. 28. Terminal Velocity – When force of drag acting on it is equal to force of gravity acting on it. Occurs during free-fall when acceleration equals zero because of air resistance.
29. 29. EQUATIONS:
30. 30. Displacement = ∆X = [Xf – Xi]
31. 31. Velocity = [∆X / ∆T] (∆X is displacement)
32. 32. With acceleration, use ∆V / time required for change.
33. 33. Speed = [∆D / ∆T] (∆D is distance)
34. 34. Acceleration = [F / M] or [∆V / ∆T]
35. 35. TNEOMS EQUATIONS (as copied from Dr. V’s website):
36. 36. Vf = Vi + aDt
37. 37. Dx = Vi Dt + ½ a Dt2
38. 38. Vf2 = Vi2 + 2aDx
39. 39. Dx – displacement. Vi – initial velocity.
40. 40. Dt – change in time. Vf – final velocity.
41. 41. A – acceleration (must be constant).
42. 42. Inertia – proportional to the mass. Heavier an object, the more inertia. A body’s mass measures its inertia.
43. 43. The inertia is the same.
44. 44. Yes, natural force.
45. 45. Yes, it still has internal force. (Inertia).
46. 46. Friction – The resistive force that keeps an object from moving.
47. 47. Earth moves in a circle because of its and the sun’s gravitational pulls. Otherwise, it would continue towards the sun.
48. 48. Mass vs. weight = Mass is one’s weight in proportion to its gravitational field. To find mass, you must multiply the weight (in kg) x 9.8 (gravity) to get the mass in kg.
49. 49. Benefit corners – Causes the passenger lean closer to you while making a turn. Newton’s Third Law – a force is exerted on an object when that object interacts with another object in its environment.
50. 50. The penny would drop. To an observer, it would fly backwards.
51. 51. Newton’s Second Law – NF = ma, or net force = mass x acceleration. The acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to the object’s mass.
52. 52. Normal Force – A force that is perpendicular to the surface upon which an object moves. NF = -mg. Also, the weight of an object + any vertical forces on the object. Gravity.
53. 53. Tension in each rope is equal to half of the object’s mass.
54. 54. Direction of friction acts in the opposite direction as the direction of motion.
55. 55. Static Friction – Happens when the force of friction is greater than the applied force; results in no motion.Kinetic Friction – Happens when the object “breaks free” and moves. The force upon the object overcomes the force of friction.
56. 56. Normal force always equals weight? No. The normal force and weight are the same only when there are no forces acting upon it.
57. 57. Because only one object is moving, the horse. The cart’s velocity = 0 until the horse pulls it.
58. 58. There is a greater force on the fly because the flyswatter has a larger mass, but the fly has the greater acceleration. (Eq = F=ma).
59. 59. Newton’s Third Law – If two objects interact, the magnitude of the force exerted on object 1 by object 2 is equal to the magnitude of the force simultaneously exerted on object 2 by object 1, and these two forces are opposite in direction.
60. 60. Units of force – N, newtons.
61. 61. EQUATIONS:
62. 62. Force: F=ma.
63. 63. Newton’s Second Law: Net force = ma.
64. 64. Coefficient of Friction: μk = Fk / Fn
65. 65. Coefficient of Static Friction: μs= Fs,max / Fn
66. 66. Force of friction: Ff = μFn
67. 67. Moment of Intertia: F= d / dt(mv)
68. 68. Units for momentum – Mos, kg-m/s, m * v
69. 69. Impulse – final momentum – initial momentum, kg-m/s, f * t,
70. 70. Conservation of Momentum – Total momentum of two objects before a collision is equal to the momentum of the two objects after collision. Momentum lost by object 1 = momentum gained by object 2.
71. 71. Vectors For Momentum:a. Head on collision (two objects move in opposite directions and collide)
72. 72. b. Back end collision (two objects moving in same direction and then collide)
73. 73. c. T-bone (two objects colliding at 90 degrees)
74. 74. Impulse is the measure of the change of momentum.
75. 75. 46. Force is proportional to time, so the more time, the smaller force at the first moment of impact.