1. Force Chapter 6

2. Force Any push or pull exerted on an object

3. System The object with the force applied

4. Environment The world surrounding the object

5. Contact Force A force that acts on an object by touching it

6. Contact Force A baseball bat striking a ball

7. Long-range Force A force that acts on an object w/o touching it

8. Long-range Force The force of gravity

9. Agent Whatever is causing the force

10. Inertia The resistance to change (in motion)

11. Equilibrium When the net forces acting on an object = zero

12. Force Vector Diagram A Diagram showing the vectors of all forces acting on an object.

13. Force Vector Diagram Weight on table Force of table on the ball

14. Draw Force Vector Diagrams of: 1)A book on a desk 2)A book being pushed across the desk 3)A book falling

15. Newton’s Laws of Motion

16. Newton’s 1 st Law An object will remain at rest or in constant straight-line motion if the net force acting on it is zero

17. Newton’s 1 st Law The velocity is constant and acceleration is zero when the net force on an object is zero

18. Newton’s 2 nd Law The acceleration of an object is directly proportioned to the net force applied to it

19. Newton’s 2 nd Law F net m a =a =a =a =

20. Newton’s 2 nd Law F net = ma

21. Newton’s 3 rd Law For every action, there is an equal & opposite reaction

22. Newton’s 3 rd Law F A on B = -F B on A

23. Drill: Write out Newton’s Laws of Motion

24. Two horizontal forces of 23.5 N & 16.5 N are acting in the same direction on a 2.0 kg object. Calculate: 1) net Force on the object 2) its acceleration

25. Two horizontal forces of 23.5 N & 16.5 N are acting in opposite directions on a 2.0 kg object. Calculate: 1) 1) net force on the object 2) its acceleration

26. Forces of 4.0 N west & 3.0 N north are acting on a 2.0 kg object. Calculate: 1) net Force on the object 2) its acceleration

27. Calculate the acceleration of a 1500 g object falling towards Earth when the F air friction is 11.7 N.

28. List Newton’s Laws of Motion

29. Types of Forces Friction Tension Normal Thrust SpringWeight

30. Friction (F f ) The contact force that acts to oppose sliding motion between surfaces Its direction is parallel & opposite the direction of sliding

31. Normal (F N ) The contact force exerted by a surface on an object Its direction is perpendicular & away from the surface

32. Spring (F sp ) A restoring force, or the push or pull a spring exerts on an object Its direction is opposite the displacement of an object at the end of a spring

33. Tension (F T ) The pull exerted by a string, rope, or cable when attached to a body & pulled taut Its direction away from the object & parallel to the string at the point of attachment

34. Thrust (F thrust ) A general term for the force that moves rockets, planes, etc Its direction is the same direction as the acceleration of the object barring any resistive forces

35. Weight (F g ) Force due the gravitational attraction between two objects like an object & the Earth Its direction is straight down towards the center of the Earth

36. Drill: Name & describe the 6 types of forces

37. Weight (F g ) Weight = F g = ma g = mg F g = W = mg

38. When an object is launched, the only forces acting upon it are the forces gravity & air friction.

39. No net force is required to keep an object in motion. Frictional forces oppose motion.

40. Inertia is not a force, but the resistance to the change in motion or momentum.

41. Air exerts huge & balanced frictional forces on an object. When in motion, the net F f of air is large.

42. Terminal Velocity The constant velocity that is reached when the force of air friction of a falling object equals its weight

43. Friction (F f ) Kinetic frictional force F f, kinetic Static frictional force F f, static

44. Draw Vector Force Diagrams of: 1) a skydiver gaining downward velocity 2) a skydiver at terminal velocity

45. Draw Vector Force Diagrams of: 3) a rope pulling a ball up at constant velocity 4) a rope accelerating a ball upwards

46. An object’s weight on Earth is 490 N. Calculate: 1) its mass 2) its weight in the moon where g moon = 1.60 m/s 2

47. An 500.0 g object on an unknown planet has a weight of 250 N. Calculate the acceleration caused by the planet’s gravity.

48. Static F f The force exerted on one surface by another when there is no relative motion

49. Kinetic F f The force exerted on one surface by another when in relative motion

50. Drill: Forces of 5.0 N west, 9.0 N east, & 3.0 N north act upon a 15 kg object. Calculate its acceleration

51. Forces acting on an object: F N = -W F A > F f F applied F g or Weight FfFfFfFf FNFNFNFN

52. Net Force (F net ) Summation of all forces acting on an object Resultant vector of all the forces

53. Net Force (F net ) F net = ma

54. Net Force (F net ) F net = F A + F B + F C + etc

55. Static F f F f, static =  s F N

56.   is proportionality constant called the frictional coefficient

57. Kinetic F f F f, kinetic =  k F N

58. A 25 N force is required to pull a 50.0 N sled down the road at a constant speed. Calculate the sliding frictional coefficient between the sled & the road.

59. A person & a sled have a total weight of 490 N. The sliding frictional coefficient between the sled & the snow is 0.10. Calculate the force required to pull the sled at constant speed.

60. Drill: Calculate the acceleration of the sled if the applied force pulling on the sled is 299 N. W = 490 N  = 0.10

61. Calculate the force required to pull a 500.0 g block with an acceleration of 3.0 m/s 2.  = 0.50

62. Periodic Motion Repetitive or vibrational motion like that of a spring, swing or pendulum

63. Simple Harmonic Motion Periodic motion in which the restoring force is directly proportional to the displacement

64. Period (T) The time required to complete one full cycle of motion

65. Amplitude Maximum displacement from the zero point or equilibrium

66. Pendulum Motion Formula T = 2  ---- l agagagag

67. Calculate the period of a pendulum with a length of 49 cm:

68. Drill: Calculate the length of the pendulum of a grandfather clock whose period is equal 1.0 second: C HW

69. Fundamental Forces Gravitational Electromagnetic Strong Nuclear Weak Nuclear

70. Calculate the force required to pull a 150 g block at a constant velocity of 180 km/hr.  = 0.20

71. A 9.8 kN car went from 0 to 25 m/s in 5.0 s.   between car & road = 0.20. Calculate the force applied by the engine of the car.

72. Drill: Calculate the force required to start a 2.0 kg block & its acceleration when moving.  s = 0.20,  k = 0.10

73. Calculate the force required to start a 2.0 kg block & calculate its acceleration when moving.  s = 0.20,  k = 0.10

74. A 6.0 kg ball is attached by a rope over a pulley to a 4.0 kg ball. 1) 1) Draw the problem. 2) 2) Calculate each ball’s acceleration

75. A 6.0 kg ball is attached by a longrope over a pulley to a 4.0 kg ball. 1) 1) Calculate air friction at max velocity

76. A 150 g baseball, was hit & came to rest in 4.0 s after going 100.0 m. Calculate: v i, a, & F f on the ball.

77. A 50.0 kg box falls off a 0.49 km cliff. 1) 1) Calculate v i, v f, a, & t. 2) 2) Calculate F f at terminal velocity

78. A 10.0 kg box falls off a 0.49 km cliff & hits the ground in 20.0 s. 1) 1) Calculate v f & a. 2) 2) Calculate F f if air friction is included

79. Calculate the force required to pull a 250 g block at a constant velocity of 360 km/hr.  = 0.30

80. Drill: Calculate the force required to accelerate a 1500 g block along the floor at 3.0 m/s 2.  = 0.25

81. A 65 kg boy & a 35 kg girl are in a tug-of-war on ice. The girl’s acceleration is 13 cm/s 2. Calculate the boy’s acceleration.

82. Calculate the apparent weight of a 50.0 kg person on a scale on an elevator descending at 2.0 m/s 2.

83. Calculate the apparent weight of a 50.0 kg person on a scale on an elevator ascending at 2.0 m/s 2.

84. Drill: Calculate the period of the pendulum on Big Ben which is 4.9 m long.

85. Calculate the force required to accelerate a 10.0 kg block straight up at 25 cm/s 2.

86. Calculate the force required to accelerate a 50.0 kg block straight up over a pulley at 5.0 m/s 2.

87. Calculate the acceleration of a system of a 55.0 kg block tied to a 45.0 kg block hanging over a pulley.

88. Calculate the frictional coefficient of a 100.0 kg block if a 150 N force causes it to accelerate at 50.0 cm/s 2.

89. Drill: Calculate the frictional coefficient of a 10.0 kg block if a 98 N force causes it to slide at 30.0 cm/s.

90. A 5.0 N force accelerates a 1000.0 g block at 45.0 cm/s 2. Calculate  K.

91. Calculate the acceleration of a system of a 200.0 kg cart on a plane tied to a 50.0 kg block hanging over a pulley.