Physics

1
Physics

• Chapter 2
• Motion In One Dimension

2
Motion In One Dimension

• All Kinds of Motion
• Perceiving motion is instinctiveyour eyes pay
  more attention to moving objects than to
  stationary ones. Movement is all around you.
• Movement travels in many directions, such as the
  straight-line path of a bowling ball in a lanes
  gutter, the curved path of a tether ball, the
  spiral of a falling kite, and the swirls of water
  circling a drain.
• A frame of reference allows measurements of
  motion.

3
Motion In One Dimension

• Movement Along a Straight Line
• A description of motion relates to position and
  time. You must be able to answer the questions of
  where and when an object is positioned to
  describe its motion.
• In the figure below, the car has moved from point
  A to point B in a specific time period.

4
Motion In One Dimension

• Picturing Motion
• 100m Dash
• Drag Race

5
Motion In One Dimension

• Picturing Motion
• Motion Diagram
• Observe and Record Changes In Motion
• Uses Pictures or Drawings

6
Motion In One Dimension

• Picturing Motion
• Motion Diagram
• Observe and Record Changes In Motion
• Uses Pictures or Drawings

7
Motion In One Dimension

• Picturing Motion
• Motion Diagram
• Observe and Record Changes In Motion
• Uses Pictures or Drawings

8
Motion In One Dimension

• Picturing Motion
• Motion Diagram
• Observe and Record Changes In Motion
• Uses Pictures or Drawings

9
Motion In One Dimension

• Picturing Motion
• Particle Model
• Dots Represent Object in Motion
• Position of Dots Indicate Changes in Motion

10
Motion In One Dimension

• Picturing Motion
• Particle Model
• Constant Velocity
• Increasing Velocity
• Decreasing Velocity

11
Motion In One Dimension

• Coordinate System
• A coordinate system tells you the location of the
  zero point of the variable you are studying and
  the direction in which the values of the variable
  increase

12
Motion In One Dimension

• Coordinate System
• For Movement Along a Straight Line
• Coordinates Would Also be in a Straight Line
• ex. Number Line

13
Motion In One Dimension

• Coordinate System
• X Y Coordinate
• Provides Origin
• The origin is the point at which both variables
  have the value zero
• Time and Position
• Position in Different Axis

14
Motion In One Dimension

• Coordinate System
• Origin
• The arrow shown in the figure represents the
  runners position, which is the separation
  between an object and the origin

15
Motion In One Dimension

• Coordinate System
• The length of how far an object is from the
  origin indicates its distance from the origin
• A position 5 m left of the origin, would be a
  negative position

16
Motion In One Dimension

• Scalar and Vector Quantities
• Scalar Quantity
• Magnitude (number and units)
• ex. 15km or 250C
• Vector Quantity
• Magnitude and Direction
• ex. 15km north or 9.8m/s2 down

17
Motion In One Dimension

• Vectors
• Represented by Arrows
• Direction of the Arrow Represents the Direction
  of the Vector
• The Length of the Arrow is Proportional to the
  Magnitude of the Vector

18
Motion In One Dimension

• Resultant
• The vector that represents the sum of the other
  two vectors is called the resultant
• The resultant always points from the tail of the
  first vector to the tip of the last vector

19
Motion In One Dimension

• Time Interval (Dt)
• Time Elapsed During Motion

20
Motion In One Dimension

• Displacement (Dd)
• The change in position during the time interval
  between ti and tf is called displacement

21
Motion In One Dimension

• Displacement (Dd)
• Displacement is equal to the final position minus
  the initial position

22
Motion In One Dimension

• Problem
• Which of the following are vectors?
• Position
• Distance
• Displacement

23
Motion In One Dimension

• Solution
• Which of the following are vectors?
• Position (vector)
• Distance (scalar)
• Displacement (vector)

24
Motion In One Dimension

• Position Time Graphs
• Graphs of an objects position and time contain
  useful information about an objects position at
  various times and can be helpful in determining
  the displacement of an object during various time
  intervals

25
Motion In One Dimension

• Position Time Graphs
• The data in the table can be presented by
  plotting the time data on a horizontal axis and
  the position data on a vertical axis, which is
  called a position-time graph

26
Motion In One Dimension

• Position Time Graphs
• To draw the graph, plot the objects recorded
  positions. Then, draw a line that best fits the
  recorded points. This line represents the most
  likely positions of the runner at the times
  between the recorded data points

27
Motion In One Dimension

• Equivalent Representations
• Words, pictorial representations, motion
  diagrams, data tables, and position-time graphs
  are all representations that are equivalent. They
  all contain the same information about an
  objects motion

28
Motion In One Dimension

• Average Speed
• The absolute value of the slope of a
  position-time graph
• The sign of the slope tells you in what direction
  the object is moving
• Scalar Quantity

29
Motion In One Dimension

• Average Velocity
• The slope of a position-time graph
• The sign of the slope tells you in what direction
  the object is moving
• Vector Quantity

30
Motion In One Dimension

• Average Velocity
• Units
• Displacement Unit of Distance
• Meter (m)
• Time
• Second (s)
• Velocity
• m/s

31
Motion In One Dimension

• Average Velocity

Using Displacement and Time
Dd change in displacement
Average of Two Velocities
32
Motion In One Dimension

• Instantaneous Velocity (v)
• Magnitude and Direction of Travel at any Given
  Instant
• The term velocity refers to instantaneous
  velocity and is represented by the symbol v

33
Motion In One Dimension

• Average Velocity on Motion Diagrams
• Although the average velocity is in the same
  direction as displacement, the two quantities are
  not measured in the same units.
• Nevertheless, they are proportionalwhen
  displacement is greater during a given time
  interval, so is the average velocity.
• A motion diagram is not a precise graph of
  average velocity, but you can indicate the
  direction and magnitude of the average velocity
  on it.

34
One Moment Please

• Solving Physics Problems
• Example Problem - Electric Current
• The potential difference, or voltage, across a
  circuit equals the current multiplied by the
  resistance in the circuit. That is, V (volts) I
  (amperes) R (ohms). What is the resistance of a
  light bulb that has a 0.75 amperes current when
  plugged into a 120-volt outlet?

35

• Solving Physics Problems
• Step 1
• Analyze the problem
• What information is given to you?
• What is the question asking for?

36

• Solving Physics Problems
• Step 2
• Identify and List Known and Unknown Variables
• I 0.75A
• V 120V
• R ?

37

• Solving Physics Problems
• Step 3
• Select the Correct Formula
• I 0.75A
• V 120V
• R ?

38

• Solving Physics Problems
• Step 4
• Re-Arrange Formula to Solve for the Unknown
• I 0.75A
• V 120V
• R ?

39

• Solving Physics Problems
• Step 5
• Solve for the Unknown Using Correct Units
• I 0.75A
• V 120V
• R 160W

40

• Solving Physics Problems
• Step 6
• Check that the Answer makes Sense
• Check that the Units are Correct

41

• Back to Your Regularly Scheduled Program

42
Motion In One Dimension

• Problem
• Light from the Sun reaches Earth in 8.3 min. The
  speed of light is 3.00x108 m/s. How far is Earth
  from the Sun?

43
Motion In One Dimension

• Solution
• v 3x108 m/s
• t 8.3 min (498s)

44
Motion In One Dimension

• Problem
• Jessica jogs several times a week and always
  keeps track of how much time she runs each time
  she goes out. One day she forgets to take her
  stopwatch with her and wonders if theres a way
  she can still have some idea of her time. As she
  passes a particular bank, she remembers that it
  is 4.3 km from her house. She knows from her
  previous training that she has a consistent pace
  of 4.0 m/s. How long has Jessica been jogging
  when she reaches the bank?

45
Motion In One Dimension

• Solution
• d 4.3km 4.3x103m
• v 4.0m/s
• t ?

46
Motion In One Dimension

• Problem
• Steffan maintains a constant velocity of 5.0
  m/s. At time t 0.0 s, Steffan is 250m from
  point A. Plot a position-time graph of Steffans
  location from point A at 10.0s intervals for 60.0
  s.

47
Motion In One Dimension

• Solution

48
Motion In One Dimension

• Problem
• Candice maintains a constant velocity of 5.0
  m/s. At time t 0.0 s, Candice is 250m from
  point A. What is Candices position from point A
  at 60.0 s?

49
Motion In One Dimension

• Solution
• 550m

50
Motion In One Dimension

• Problem
• Jeb maintains a constant velocity of 5.0 m/s. At
  time t 0.0 s, Jeb is 250m from point A. What
  is the displacement from the starting position at
  60.0 s?

51
Motion In One Dimension

• Solution
• 550m - 250m 3.0x102 m

52
Motion In One Dimension

• Problem
• This graph shows position-time graphs for Joszi
  and Heike paddling canoes in a local river. At
  what time(s) are Joszi and Heike in the same
  place?

53
Motion In One Dimension

• Solution
• 1.0h

54
Motion In One Dimension

• Problem
• This graph shows position-time graphs for Joszi
  and Heike paddling canoes in a local river. How
  much time does Joszi spend on the river before he
  passes Heike?

55
Motion In One Dimension

• Solution
• 45 min.

56
Motion In One Dimension

• Problem
• This graph shows position-time graphs for Joszi
  and Heike paddling canoes in a local river.
  Where on the river does it appear that there
  might be a swift current?

57
Motion In One Dimension

• Solution
• from 6.0 to 9.0 km from the origin

58
Motion In One Dimension

• Problem
• This graph shows the position-time graph
  depicting Donnys movement up and down the aisle
  at a store. The origin is at one end of the
  aisle. Describe Donnys movements at the store
  that would correspond to the motion represented
  by the graph.

59
Motion In One Dimension

• Solution

60
Motion In One Dimension

• Problem
• This graph shows the position-time graph
  depicting Bens movement up and down the aisle at
  a store. The origin is at one end of the aisle.
  When does Ben have a position of 6.0 m?

61
Motion In One Dimension

• Solution
• From 7.0 to 24.0 s, at 43.0 s, and from 53.0 to
  56.0 s

62
Motion In One Dimension

• Problem
• This graph shows the position-time graph
  depicting Jessicas movement up and down the
  aisle at a store. The origin is at one end of
  the aisle. How much time passes between when
  Jessica enters the aisle and when she gets to a
  position of 12.0 m?

63
Motion In One Dimension

• Solution
• t 33s

64
Motion In One Dimension

• Problem
• This graph shows the position-time graph
  depicting Chriss movement up and down the aisle
  at a store. The origin is at one end of the
  aisle. What is Chriss average velocity between
  37.0 s and 46.0 s?

65
Motion In One Dimension

• Solution

66
Motion In One Dimension

• Homework
• Page 69 - 70
• Problems
• 9 (10.1km)
• 12 (a, 70.0m b, 140.0m c, 14m d, 28m)
• 15 (0.2km W)

67
Motion In One Dimension

• Acceleration
• Gives You the Feeling of Being Pushed
• Change in Velocity over a Period of Time
• Compare
• 0 Velocity
• Constant Velocity
• Increasing Velocity
• Decreasing Velocity

68
Motion In One Dimension

• Acceleration
• The Slope of a Velocity Time Graph

69
Motion In One Dimension

• Acceleration
• Change in Velocity over a Period of Time

70
Motion In One Dimension

• Acceleration
• Units
• Velocity m/s
• Time Second
• Acceleration m/s/s or m/s2

71
Motion In One Dimension

• Negative Acceleration
• Acceleration can be Positive or Negative
• There is No Such Thing as Deceleration
• When Dv is Negative, Acceleration Will be Negative

72
Motion In One Dimension

• Calculating Velocity from Acceleration

73
Motion In One Dimension

• Displacement Under Constant Acceleration

74
Motion In One Dimension

• Velocity Under Constant Acceleration

75
Motion In One Dimension

• Free Fall
• Acceleration Due to Gravity ONLY!
• Galileo concluded that, neglecting the effect of
  the air, all objects in free fall had the same
  acceleration. It didnt matter what they were
  made of, how much they weighed, what height they
  were dropped from, or whether they were dropped
  or thrown.

76
Motion In One Dimension

• Free Fall
• The acceleration of falling objects, given a
  special symbol, g, is equal to 9.80 m/s2.
• The acceleration due to gravity is the
  acceleration of an object in free fall that
  results from the influence of Earths gravity
  only.

77
Motion In One Dimension

• Free Fall

78
Motion In One Dimension

• Free Fall
• At the top of the flight, the balls velocity is
  0m/s. What would happen if its acceleration were
  also zero? Then, the balls velocity would not be
  changing and would remain at 0 m/s.

79
Motion In One Dimension

• Free Fall
• If this were the case, the ball would not gain
  any downward velocity and would simply hover in
  the air at the top of its flight.

80
Motion In One Dimension

• Free Fall
• Because this is not the way objects tossed in the
  air behave on Earth, you know that the
  acceleration of an object at the top of its
  flight must not be zero. Further, because you
  know that the object will fall from that height,
  you know that the acceleration must be downward.

81
Motion In One Dimension

• Free Fall
• Amusement parks use the concept of free fall to
  design rides that give the riders the sensation
  of free fall.
• These types of rides usually consist of three
  parts the ride to the top, momentary suspension,
  and the plunge downward.
• When the cars are in free fall, the most massive
  rider and the least massive rider will have the
  same acceleration

82
Motion In One Dimension

• Free Fall
• The Acceleration of Gravity is just another form
  of Acceleration
• The Formulas for Acceleration Apply to the
  Acceleration of Gravity

83
Motion In One Dimension

• Problem
• Find the uniform acceleration that causes a cars
  velocity to change from 32m/s to 96m/s in an 8.0s
  period.

84
Motion In One Dimension

• Solution
• vi 32m/s
• vf 96m/s
• Dt 8.0s
• a ?

85
Motion In One Dimension

• Problem
• Use the velocity-time graph of a moving object to
  determine what the acceleration of the object was
  during the first 5.0s of travel?

86
Motion In One Dimension

• Solution
• vi 0.0m/s
• vf 30.0m/s
• Dt 5.0s
• a ?

87
Motion In One Dimension

• Problem
• Use the velocity-time graph of a moving object to
  determine what the acceleration of the object was
  between 5.0s and 10.0s?

88
Motion In One Dimension

• Solution
• vi 30.0m/s
• vf 30.0m/s
• ti 5.0s
• tf 10.0s
• a ?

89
Motion In One Dimension

• Problem
• Use the velocity-time graph of a moving object to
  determine what the acceleration of the object was
  between 10.0s and 15.0s?

90
Motion In One Dimension

• Solution
• vi 30.0m/s
• vf 20.0m/s
• ti 10.0s
• tf 15.0s
• a ?

91
Motion In One Dimension

• Problem
• Use the velocity-time graph of a moving object to
  determine what the acceleration of the object was
  between 20.0s and 25.0s?

92
Motion In One Dimension

• Solution
• vi 20.0m/s
• vf 0.0m/s
• ti 20.0s
• tf 25.0s
• a ?

93
Motion In One Dimension

• Problem
• Determine the final velocity of a proton that has
  an initial velocity of 2.35x105m/s and then is
  accelerated uniformly in an electric field at the
  rate of -1.10x1012 m/s2 for 1.50x10-7s.

94
Motion In One Dimension

• Solution
• vi 2.35x105m/s
• vf ?
• Dt 1.50x10-7s
• a -1.10x1012 m/s2

95
Motion In One Dimension

• Problem
• A supersonic jet flying at 145m/s experiences
  uniform acceleration at the rate of 23.1m/s2 for
  20.0s. What is its final velocity?

96
Motion In One Dimension

• Solution
• vi 145m/s
• vf ?
• Dt 20.0s
• a 23.1m/s2

97
Motion In One Dimension

• Problem
• A supersonic jet flying at 145m/s experiences
  uniform acceleration at the rate of 23.1m/s2 for
  20.0s. The speed of sound in air is 331m/s.
  What is the planes speed in terms of the speed
  of sound? (Mach ?)

98
Motion In One Dimension

• Solution
• vi 145m/s
• vf 607m/s
• Dt 20.0s
• a 23.1m/s2
• sound barrier 331m/s

99
Motion In One Dimension

• Problem
• A dragster starting from rest accelerates at
  49m/s2. How fast is it going when it has traveled
  325m?

100
Motion In One Dimension

• Solution
• vi 0m/s
• vf ?
• a 49m/s2
• d 325m

101
Motion In One Dimension

• Problem
• A race car can be slowed with a constant
  acceleration of -11m/s2. If the car is going
  55m/s, how many meters will it travel before it
  stops?

102
Motion In One Dimension

• Solution
• vi 55m/s
• vf 0.0m/s
• Dt
• a -11m/s2
• d ?

103
Motion In One Dimension

• Problem
• Determine the displacement of a plane that
  experiences uniform acceleration from 66m/s to
  88m/s in 12s.

104
Motion In One Dimension

• Solution
• vi 66m/s
• vf 88m/s
• Dt 12s
• a
• d ?

105
Motion In One Dimension

• Problem
• A speeding car is traveling at a constant speed
  of 30.0m/s when it passes a stopped police car.
  The police car accelerates at 7.0m/s2. How fast
  will it be going when it catches up with the
  speeding car?

106
Motion In One Dimension

• Solution
• vs 30m/s
• vpi 0m/s
• a 7.0m/s2
• Dt ?
• vpf ?

107
Motion In One Dimension

• Solution
• vs 30m/s
• vpi 0m/s
• a 7.0m/s2
• Dt ?
• vpf ?

108
Motion In One Dimension

• Solution
• vs 30m/s
• vpi 0m/s
• a 7.0m/s2
• Dt ?
• vpf ?

109
Motion In One Dimension

• Solution
• vs 30m/s
• vpi 0m/s
• vpf ?
• Dt 8.6s
• a 7.0m/s2

110
Motion In One Dimension

• Homework
• Page 71 - 72
• Problems
• 21 (8.6m/s)
• 27 (110m)
• 31 (a, 20s b,???)
• 40 (0.60s)
• 42 (a, 0.20s b, 0.06s 0.34s c, ??? d, ???)

111

• Lets Talk About Labs
• Components of a Good Lab Paper

112

• Lab
• Components of a Good Lab Paper
• Title
• Clearly Presents Research Concept

113

• Lab
• Components of a Good Lab Paper
• Abstract
• Brief Summary of the Research Performed
• Background
• Hypothesis
• Significant Results
• Conclusions
• Usually 1 2 Paragraphs
• Usually Written After the Research is Complete

114

• Lab
• Components of a Good Lab Paper
• Introduction
• Explanation of the Experiment
• Why?
• Background
• Specific Purpose
• Hypothesis

115

• Lab
• Components of a Good Lab Paper
• Materials and Methods
• Identify Precisely How the Experiment is to be
  Performed
• What Materials are Used
• How was the Experiment Performed
• Where and When was the Experiment Performed
• With this Information Others Should be Able to
  Repeat Your Experiment and Obtain Similar Results

116

• Lab
• Components of a Good Lab Paper
• Results
• Present Data
• Accurately Collected
• Calculations (Units!)
• Only Data No Conclusions!
• Tables and/or Graphs
• Sometimes Presented in Text and Displayed in an
  Appendix

117

• Lab
• Components of a Good Lab Paper
• Discussion / Conclusions
• Detailed Explanation of How Your Results
  Supported Your Hypothesis (Or Not)
• Your Chance to Present Your Case
• Interpret Your Data
• Suggest Improved Experimental Design
• Further Possibilities for Research?