Force and it's effects

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 1st 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 1st Law
The velocity is
constant and
acceleration is zero
when the net force on
an object is zero

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

19. Newton’s 2nd Law
Fnet
m
a =

20. Newton’s 2nd Law
Fnet = ma

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

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

23. 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

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

25. 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

26. Calculate the
acceleration of a 1500
g object falling
towards Earth when
the Fair friction is 11.7 N.

27. List Newton’s
Laws of
Motion

28. Types of Forces
Friction Tension
Normal Thrust
Spring Weight

29. Friction (Ff)
•The contact force that acts to
oppose sliding motion
between surfaces
•Its direction is parallel &
opposite the direction of
sliding

30. Normal (FN)
•The contact force exerted
by a surface on an object
•Its direction is
perpendicular & away
from the surface

31. Spring (Fsp)
•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

32. Tension (FT)
• 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

33. Thrust (Fthrust)
• 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

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

35. Name &
describe the 6
types of forces

36. Weight (Fg)
Weight = Fg = mag = mg
Fg = W = mg

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

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

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

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

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

42. Friction (Ff)
Kinetic frictional force
Ff, kinetic
Static frictional force
Ff, static

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

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

45. An object’s weight on
Earth is 490 N. Calculate:
1) its mass
2) its weight in the moon
where gmoon = 1.60 m/s2

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

47. Static Ff
•The force exerted on
one surface by
another when there is
no relative motion

48. Kinetic Ff
•The force exerted on
one surface by
another when in
relative motion

49. Forces acting on an object:
FN = -W
FA > Ff
Fapplied
Fg or Weight
Ff
FN

50. Static Ff
Ff, static = msFN

51. m
ms is proportionality
constant called the
frictional coefficient

52. Kinetic Ff
Ff, kinetic = mkFN

53. 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.

54. 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.

55. Calculate the acceleration
of the sled if the applied
force pulling on the sled
is 299 N.
W = 490 N
m = 0.10

56. Calculate the force
required to pull a 500.0
g block with an
acceleration of 3.0 m/s2.
m = 0.50

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

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

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

60. Amplitude
•Maximum
displacement from
the zero point or
equilibrium

61. Pendulum Motion
Formula
T = 2p ----
l
ag

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

63. Calculate the length
of the pendulum of a
grandfather clock
whose period is equal
1.0 second:

64. Fundamental Forces
•Gravitational
•Electromagnetic
•Strong Nuclear
•Weak Nuclear

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

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

67. Calculate the force
required to start a 2.0 kg
block & its acceleration
when moving.
ms = 0.20, mk = 0.10

68. Calculate the force
required to start a 2.0 kg
block & calculate its
acceleration when
moving.
ms = 0.20, mk = 0.10

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

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

71. A 65 kg boy & a 35 kg
girl are in a tug-of-war.
The girl’s acceleration
is 13 cm/s2. Calculate
the boy’s acceleration.

72. A 150 g baseball, was hit
& came to rest in 4.0 s
after going 100.0 m.
Calculate: vi, a, & Ff on
the ball.

73. A 50.0 kg box falls off a
0.49 km cliff.
1) Calculate vi, vf, a, & t.
2) Calculate Ff if air
friction is included

74. A 10.0 kg box falls off a
0.49 km cliff & hits the
ground in 20.0 s.
1) Calculate vf & a.
2) Calculate Ff if air
friction is included

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

76. Calculate the force
required to accelerate
a 1500 g block along
the floor at 3.0 m/s2.
m = 0.25

77. Calculate the apparent
weight of a 50.0 kg
person on a scale on
an elevator descending
at 2.0 m/s2.

78. Calculate the
apparent weight of a
50.0 kg person on a
scale on an elevator
ascending at 2.0 m/s2.

79. Calculate the period
of the pendulum on
Big Ben which is 4.9
m long.

80. Calculate the force
required to accelerate
a 10.0 kg block
straight up at
25 cm/s2.

81. Calculate the force
required to accelerate
a 50.0 kg block
straight up over a
pulley at 5.0 m/s2.

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

83. Calculate the frictional
coefficient of a 100.0
kg block if a 150 N
force causes it to
accelerate at 50.0 cm/s2.

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

85. A 5.0 N force
accelerates a 1000.0 g
block at 45.0 cm/s2.
Calculate mK.

86. 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.