Download You get to explore the possible energy transitions for Hydrogen

Astronomy 1020
Stellar Astronomy
Spring_2016
Day-9
Course Announcements
•
SW-2 … will download scores on Monday.
SW-3 & 4 will be due soon-ish (Fri. Feb. 12)
1st set of Dark Sky observing nights:
•
•
•
•
Mon. Feb. 8 – 7:30pm at the observatory.
Tues. Feb. 9 is the weather backup if both are cancelled.
•
Exam-1: Friday Feb. 12 (ch. 1-4)
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First, 1st Quarter observing nights: Mon. @ 7:30pm
Lab This Week
•
Hydrogen Energy Levels
•
What you need to know:
You get to explore the possible energy
transitions for Hydrogen.
Reading ahead in Chapter 5 will help.
•
•
Hydrogen
Spectrum
Hydrogen Spectrum
Newton’s First
Law of Motion
• A body remains at rest or moves in a straight line at
a constant speed unless acted upon by an outside
(net) force.
• A rockets will coast in space along a straight line at
constant speed.
• A hockey puck glides across the ice at constant
speed until it hits something
Newton’s Second
Law of Motion
• (net)Force = mass x acceleration or
Fnet = m x a
• Acceleration is the rate of change in velocity – or
how quickly your motion is changing.
• Three accelerators in your car!!
Newton’s Third
Law of Motion
• Whenever one body exerts a force on a second
body, the second body exerts an equal and opposite
force on the first body.
• Don’t need a rocket launch pad!
• The Bug and the Windshield – who is having the
worse day?
Newton’s Laws of Motion &
Gravitation
• All my favorite Projectiles behave like this!!!

Velocity
Force
Acceleration
 The gravitational
force results in an
acceleration.
 All objects on Earth
fall with the same
acceleration known
as g.
 g = 9.8 m/s2
F
g
w
eight m
 Orbits describe one body
falling around another.
 The less massive object
is a satellite of the more
massive object.
 The two bodies orbit a
common center of mass.
 For a much smaller
satellite, the center of
mass is inside the more
massive body.
 An astronaut inside an
orbiting space shuttle
will experience free fall
because he is falling
around Earth at the
same rate as the shuttle.
 He is not weightless.
 Gravity provides the
centripetal force that
holds a satellite in its
orbit.
 Uniform circular
motion: moving on a
circular path
at constant speed.
 Still experiencing an
acceleration since the
direction is constantly
changing.
 Circles and ellipses are bound orbits.
 Objects with higher orbital speeds can
escape bound orbits to be in unbound orbits.
 Parabolas and hyperbolas are examples.
Newton’s Law of Gravitation
• Newton’s law of gravitation states: Two bodies
attract each other with a force that is directly
proportional the product of their masses and is
inversely proportional to the square of the distance
between them.

Gm
m
1
2
F

grav
2
d
What the ….? I thought I understood gravity?
Newton’s Law of Gravitation
• To figure out the gravitational force just multiply the
mass of the two things together then divide by the
distance they are apart (squared).

Gm
m
1 2
F

grav
2
d
m1
d
m2