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Charles Hakes

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Title: Charles Hakes


1
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2
Chapter 1
  • Newton
  • and Gravity

3
Outline
  • Notes
  • Kepler Review
  • Newtons laws
  • Gravity
  • Tutoring Berndt 610, 640 late afternoons (Katy,
    Shane, Luke)

4
Review
  • African or European?
  • Other favorite answers
  • The speed of light.
  • I dont know - Im not king!
  • My Holy hand grenade blew it up
  • 42 (mixing your fiction).
  • Im from Oklahoma and have no clue
  • for a chimney swallow while hunting mosquitoes.

5
Group Exercise
  • Assume a comet has a period of 5.2 years, with
    eccentricity very close to 1.

6
Group Exercise
  • Assume a comet has a period of 5.2 years, with
    eccentricity very close to 1.
  • Calculate the semi-major axis.

7
Group Exercise
  • Assume a comet has a period of 5.2 years, with
    eccentricity very close to 1.
  • Calculate the semi-major axis.
  • p2 a3
  • What is the major axis?
  • What is the maximum distance this comet might
    ever get from the Sun?
  • Include copy of work in your folder.

8
Figure 1.20Isaac Newton (1642-1727)
9
An iron weight and a styrofoam ball are dropped
from the same height at the same time.
  • Which hits the ground first?
  • A) The iron weight
  • B) The styrofoam ball
  • C) They hit at the same time

10
Newtons Laws
11
Newtons 1st Law
  • If there are no external forces on an object,
    then
  • If it is at rest, it will stay that way -
    forever.
  • If it is moving, it will keep doing so at
    constant velocity, in a straight line - forever.

12
Newtons 1st Law
  • Inertia - the natural tendency of an object to
    stay at rest, or remain moving with a constant
    velocity.
  • Mass is a quantitative measure of inertia.

13
Momentum
  • Momentum - the product of mass and velocity.
  • momentum mass x velocity
  • A concept related to Inertia
  • Momentum (both linear and angular) must be
    conserved.

14
Which object has the most momentum?
  • A) A cruise missile
  • B) A ship
  • C) A glacier
  • D) Need more information

15
Which object has the most momentum?
  • A - A cruise missile
  • 1000 kg
  • 100m/s
  • B - A ship
  • 10 million kg 107 kg
  • 10 m/s
  • C - A glacier
  • 1012 kg
  • 1 m/day (10-5 m/s)

16
Which object has the most momentum?
  • A - A cruise missile
  • B - A ship
  • C - A glacier

17
Angular momentum demonstration
18
Angular momentum demonstration
  • This is why planets move faster closer to the sun.

19
Newtons 2nd Law
  • The net force on an object is equal to the mass
    of the object times the acceleration of the
    object
  • Fnet m a
  • The SI units of force are newtons (N).

20
Newtons 2nd Law
  • Force - something that is capable of changing an
    objects state of motion (its velocity)
  • Fnet - the sum of all forces on an object
  • Dynamics - the study of changes in motion and
    what causes those changes

21
Newtons 2nd Law
  • Fnet m a

22
Newtons 3rd Law
  • the one hard to believe

23
A brick hits a glass window. The brick breaks
the glass, so the magnitude of the force of the
brick on the glass is
  • A is greater than the magnitude of the force of
    the glass on the brick
  • B is smaller than the magnitude of the force of
    the glass on the brick
  • C is equal to the magnitude of the force of the
    glass on the brick
  • D none of the preceding

24
Newtons 3rd Law
  • For every action (force) there is an equal and
    opposite reaction (force).
  • Important note - the action-reaction force pairs
    do NOT act on the same object.

25
A brick hits a glass window. The brick breaks
the glass, so the magnitude of the force of the
brick on the glass is
  • A is greater than the magnitude of the force of
    the glass on the brick
  • B is smaller than the magnitude of the force of
    the glass on the brick
  • C is equal to the magnitude of the force of the
    glass on the brick
  • D none of the preceding

26
Gravity
27
Figure 1.22Gravity
28
Figure 1.24Suns Gravity
29
Gravity
  • Any object having Mass will exert a gravitational
    force on other massive objects.
  • Force is proportional to mass of each object
  • F ? M1 M2

30
Gravity
  • Any object having Mass will exert a gravitational
    force on other massive objects.
  • Force is proportional to mass of each object
  • Force decreases with the square of the distance
    between the two objects
  • F ? M1 M2 / r2

31
Figure 1.23Gravitational Force
  • Any object having Mass will exert a
    gravitational force on other massive objects.
  • F ? M1 M2 / r2

32
Gravity
  • Any object having Mass will exert a gravitational
    force on other massive objects.
  • Force is proportional to mass of each object
  • Force decreases with the square of the distance
    between the two objects
  • Proportionality constant is G, the universal
    gravitational constant
  • G 6.67x10-11 (N m2/kg2)
  • F G M1 M2 / r2

33
Gravity
  • F G M1 M2 / r2

34
Newton
  • Modification to Keplers 1st Law
  • Both the Sun and the planet orbit about the
    center of mass of the system.

35
Figure 1.25Orbits
36
Newton
  • Modification to Keplers 3rd Law
  • That math law - updated
  • P2 (years) a3 (astronomical units)
    Mtotal(solar units)
  • For planets around the Sun, this makes very
    little difference except for (even for) Jupiter
    (0.1 Msun)

37
Which mass pair has the greatest gravitational
force between them?
  • 1 A 5Msolar mass and a 4Msolar mass separated by
    4 AU.
  • 2 A 4Msolar mass and a 3Msolar mass separated by
    3 AU.
  • 3 A 3Msolar mass and a 2Msolar mass separated by
    2 AU.
  • 4 A 2Msolar mass and a 1Msolar mass separated by
    1 AU.

38
Which mass pair has the greatest gravitational
force between them?
  • 1 A 5Msolar mass and a 4Msolar mass separated by
    4 AU.
  • 2 A 4Msolar mass and a 3Msolar mass separated by
    3 AU.
  • 3 A 3Msolar mass and a 2Msolar mass separated by
    2 AU.
  • 4 A 2Msolar mass and a 1Msolar mass separated by
    1 AU.

39
Group Exercise
  • Calculate the force between those two masses.
  • A 2Msolar mass and a 1Msolar mass separated by 1
    AU.

40
Three Minute Paper
  • Write 1-3 sentences.
  • What was the most important thing you learned
    today?
  • What questions do you still have about todays
    topics?

41
Review
  • What was the most important thing you learned?
  • A circle is actually a special kind of ellipse
    with only one focal point
  • A square is to a rectangle as a circle is to an
    ellipse
  • The semi-major axis is half of the major axis.
  • If the semi-major axis of two bodies is the same,
    they take the same amount of time to orbit.

42
Review
  • What was the most important thing you learned?
  • Planets move faster when closer to the sun
  • The closer the focus points, the more like a
    circle the orbit becomes.
  • The eccentricity of the ellipse is the ratio of
    the distance between the foci to the length of
    the major axis.

43
Review
  • Did not get thrown into the abyss. (i.e.
    Remembered Their Monty Python) 3 Other
    memorable answers
  • I dont know - Im not king!
  • zero???
  • My Holy hand grenade blew it up
  • Im from Oklahoma and have no clue
  • for a chimney swallow while hunting mosquitoes.
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