![Page 1: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/1.jpg)
Gravity• Galileo’s observations on gravity led to Newto
n’s Law of Gravitation and the three Laws of Motion
• Objects fall at the same rate regardless of mass because more massive objects have more inertia or resistance to motion
• Fgrav = G (m1 x m2) / r2
• Force of gravity between two masses is proportional to the product of masses divided by distance squared ‘inverse square law’
![Page 2: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/2.jpg)
Newton – Three Laws of Motion
1. Inertia2. F = ma3. Action = Reaction
![Page 3: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/3.jpg)
Newton’s Laws of Motion
• Law of Inertia: A body continues in state of rest or motion unless acted on by an external force; Mass is a measure of inertia
• Law of Acceleration: For a given mass m, the acceleration is proportional to the force applied
F = m a
• Law of Action equals Reaction: For every action there is an equal and opposite reaction; momemtum (mass x velocity) is conserved
![Page 4: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/4.jpg)
Velocity, Speed, Acceleration
• Velocity implies both speed and direction; speed may be constant but direction could be changing, and hence accelerating
• Acceleration implies change in speed or direction or both
• For example, stone on a string being whirled around at constant speed; direction is constantly changing therefore requires force
![Page 5: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/5.jpg)
Ball Swung around on a String:
Same Speed,(in uniform circular motion)
Changing Direction(swinging around the circle)
![Page 6: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/6.jpg)
Ball Swung around on a String:
Same Speed,(in uniform circular motion)
Changing Direction(swinging around the circle)
![Page 7: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/7.jpg)
Donut Swung around on a String
Force
Acceleration
![Page 8: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/8.jpg)
Donut Swung around on a String
Force
Acceleration
![Page 9: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/9.jpg)
Conservation of momemtum:action equal reaction
• The momemtum (mv) is conserved before and after an event
• Rocket and ignited gases: M(rocket) x V(rocket) = m(gases) x v(gases)• Two billiard balls: m1 v1 + m2 v2 = m1 v1’ + m2 v2’ v1,v2 – velocities before collision v1’,v2’ – velocities after collision• Example – you and your friend (twice as
heavy) on ice!
![Page 10: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/10.jpg)
Conservation of momemtum:action equal reaction
• The momemtum (mv) is conserved before and after an event
• Rocket and ignited gases: M(rocket) x V(rocket) = m(gases) x v(gases)• Two billiard balls: m1 v1 + m2 v2 = m1 v1’ + m2 v2’ v1,v2 – velocities before collision v1’,v2’ – velocities after collision• Example – you and your friend (twice as
heavy) on ice!
![Page 11: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/11.jpg)
Force = (apple’s mass) (acceleration due to gravity)
Equal and OppositeForce from the Table
Net Force is Zero, No Net Motion
Action = Reaction
![Page 12: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/12.jpg)
Force = (apple’s mass) (acceleration due to gravity)
Equal and OppositeForce from the Table
Net Force is Zero, No Net Motion
Action = Reaction
![Page 13: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/13.jpg)
Acceleration due to gravity• Acceleration is rate of change of velocity, speed or
direction of motion, with time a = v/t• Acceleration due to Earth’s gravity : a g g = 9.8 m per second per second, or 32 ft/sec2
• Speed in free-fall T (sec) v (m/sec) v (ft/sec) 0 0 0 1 9.8 32 2 19.6 64 3 29.4 96 60 mi/hr = 88 ft/sec (between 2 and 3 seconds)
![Page 14: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/14.jpg)
Galileo’s experiment revisited• What is your weight and mass ?• Weight W is the force of gravity acting
on a mass m causing acceleration g• Using F = m a, and the Law of Gravitation
W = m g = G (m MEarth) /R2
(R – Radius of the Earth) The mass m of the falling object cancels
out and does not matter; therefore all objects fall at the same rate or acceleration
g = GM / R2
i.e. constant acceleration due to gravity 9.8 m/sec2
![Page 15: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/15.jpg)
Galileo’s experiment on gravity• Galileo surmised that time differences
between freely falling objects may be too small for human eye to discern
• Therefore he used inclined planes to slow down the acceleration due to gravity and monitor the time more accurately
v
Changing the angle of the incline changes the velocity v
![Page 16: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/16.jpg)
‘g’ on the Moon g(Moon) = G M(Moon) / R(Moon)2
G = 6.67 x 10-11 newton-meter2/kg2
M(Moon) = 7.349 x 1022 Kg R(Moon) = 1738 Km
g (Moon) = 1.62 m/sec/sec About 1/6 of g(Earth); objects on the
Moon fall at a rate six times slower than on the Earth
![Page 17: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/17.jpg)
Escape Velocity and Energy• To escape earth’s gravity an object must have
(kinetic) energy equal to the gravitational (potential) energy of the earth
• Kinetic energy due to motion K.E. = ½ m v2
• Potential energy due to position and force P.E. = G m M(Earth) / R (note the similarity with the Law of Gravitation)• Minimum energy needed for escape: K.E. = P.E. ½ m v2 = G m M / R Note that the mass m cancels out, and• v (esc) = 11 km/sec = 7 mi/sec = 25000 mi/hr The escape velocity is the same for all objects of
mass m
![Page 18: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/18.jpg)
Escape Velocity and Energy• To escape earth’s gravity an object must have
(kinetic) energy equal to the gravitational (potential) energy of the earth
• Kinetic energy due to motion K.E. = ½ m v2
• Potential energy due to position and force P.E. = G m M(Earth) / R (note the similarity with the Law of Gravitation)• Minimum energy needed for escape: K.E. = P.E. ½ m v2 = G m M / R Note that the mass m cancels out, and• v (esc) = 11 km/sec = 7 mi/sec = 25000 mi/hr The escape velocity is the same for all objects of
mass m
![Page 19: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/19.jpg)
Object in orbit Continuous fall !
Object falls towards the earth at the same rate as the earth curves away from it
![Page 20: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/20.jpg)
![Page 21: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/21.jpg)
![Page 22: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/22.jpg)
Conservation of angular momentum says that product of radius r and momentum mv must be constant radius times rotation rate (number of rotations per second) is constant
Angular Momentum
![Page 23: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/23.jpg)
Angular Momentum
• All rotating objects have angular momentum
• L = mvr ; acts perpendicular to the plane of rotation
• Examples: helicopter rotor, ice skater, spinning top or wheel (experiment)
• Gyroscope (to stabilize spacecrafts) is basically a spinning wheel whose axis maintains its direction; slow precession like the Earth’s axis along the Circle of Precession
![Page 24: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/24.jpg)
Conservation of Angular Momentum
• Very important in physical phenomena observed in daily life as well as throughout the Universe. For example,
• Varying speeds of planets in elliptical orbits around a star
• Jets of extremely high velocity particles, as matter spirals into an accretion disc and falls into a black hole
![Page 25: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/25.jpg)
Relativistic1 Jet “From” Black Hole
1. “Relativistic velocities are close to the speed of light
![Page 26: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/26.jpg)
![Page 27: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/27.jpg)
Quiz 1• Each quiz sheet has a different 5-digit
symmetric number which must be filled in (as shown on the transparency, but NOT the same one!!!!!)
• Please hand in both the exam and the answer sheets with your name on both
• Question/answer sheets will be handed back on Wednesday after class
• Please remain seated until we begin collecting (20-25 minutes after start)
• Class after quiz
![Page 28: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/28.jpg)
![Page 29: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/29.jpg)
Stars and Galaxies: Galileo to HST
•http://thenextdigit.com/16961/nasa-telescopes-new-panoramic-view-andromeda-resolves-stars/
![Page 30: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/30.jpg)
Why is the sky blue ?
The atmosphere scatters the blue light more than red light
![Page 31: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/31.jpg)
Light and Matter• Light is electromagnetic energy, due to
interaction of electrical charges• Matter is made of atoms – equal number
of positive and negative particles• An atom is the smallest particle of an
element; natural element H to U• Atom Nucleus (protons + neutrons),
with ‘orbiting’ electrons• No. of protons in nucleus = Atomic
Number• Science of light Spectroscopy
![Page 32: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/32.jpg)
Radiation and Spectroscopy
• Light is electromagnetic energy
• Propagates as both particles and waves
• Photons – particles of light
• Wavelength = Velocity / Frequency
![Page 33: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/33.jpg)
Light is electromagnetic wave;Does not require a medium to propagate,
unlike water or sound
Wavelength is the distance between successive crests or troughs
![Page 34: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/34.jpg)
Wavelength ()
Speed (c)
Frequency (f) (# waves/second)
Speed = wavelength x frequency c = fFrequency ‘f’ is the number of waves passing a point per second
WAVES: Frequency, Wavelength, Speed
![Page 35: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/35.jpg)
Units of wavelength and frequency
• Frequency is the number of cycles per second• Since speed of light is constant, higher the
frequency the shorter the wavelength and vice-versa
• Wavelengths are measured in Angstroms: 1A = 1/100,000,000 cm = 1/10 nanometer (nm)
• The higher the frequency the more energetic the wave
• Wavelength (or frequency) defines radiation or color
![Page 36: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/36.jpg)
Spectrum
Prism
WhiteLight
Prisms disperse light into its component colors: Red-Violet
![Page 37: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/37.jpg)
Visible Light
• Forms a narrow band within the electromagnetic spectrum ranging from gamma rays to radio waves
• Human eye is most sensitive to which color?
• Yellow. Why?
![Page 38: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/38.jpg)
Light: Electromagnetic SpectrumFrom Gamma Rays to Radio Waves
Gamma rays are the most energetic (highest frequency, shortest wavelength),Radio waves are the least energetic.
Gamma
X-Ray
UV
Visible
![Page 39: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/39.jpg)
DecreasingWavelength ORIncreasingFrequency
![Page 40: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/40.jpg)
Visible light spectrum: Each color is defined by its wavelength, frequency or energy
Red - Blue 7000 - 4000 Angstroms ( 1 nm = 10 A, 1 A = 10-8 cm)Blue light is more energetic than red light
Light also behaves like ‘particles’ called photons Photon energy, frequency, wavelength: E = h f = hc/ Planck’s Law (‘h’ is a number known as Planck’s constant)
![Page 41: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/41.jpg)
Matter and Particles of Light: Quantum Theory
• Light (energy) and matter in motion behave both as waves and particles
• Wave-Particle Duality - Quantum Theory • Particles of light are called photons: E = hf = hc/• Photons of a specific wavelength may be absorbed
or emitted by atoms in matter• Matter is made of different natural elements: lightest
Hydrogen (1 proton), heaviest Uranium (92 protons)• Smallest particle of an element is atom, made up of a
nucleus (protons and neutrons), and orbiting electrons• Electrons and protons attract as opposite electrical
charges, NOT gravitationally like planets and Sun
![Page 42: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/42.jpg)
![Page 43: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/43.jpg)
The Hydrogen Atom
Electron orbitsDiscrete energies
![Page 44: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/44.jpg)
Absorption of light (energy) photon by H-atom
![Page 45: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/45.jpg)
Emission of light photon by H-atomphoton energy color
![Page 46: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/46.jpg)
![Page 47: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/47.jpg)
![Page 48: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/48.jpg)
Series of spectral lines of Hydrogen
![Page 49: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/49.jpg)
Wavelengths of series of lines from Hydrogen
![Page 50: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/50.jpg)
SPECTRAL SIGNATURE OF ELEMENTS
![Page 51: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/51.jpg)
Continuous, Absorption, and Emission Spectra
![Page 52: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/52.jpg)
Brightness and Temperature
• Brightness is related to the total energy emitted, or the luminosity of an object
• The energy emitted is related to the temperature of the object
• B = T4 is a constant)
Stefan-Boltzmann Law
![Page 53: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/53.jpg)
Color Indicates Temperature and Energy of the Source
Objects generally emit radiation at all wavelengths, but mostly at one peak Wavelength depending on their temperature (e.g. blue – hot, red – cool)
Surface T (Sun) = 5600 K “ (Mercury) = 800 K
Blackbody: Perfectabsorber and emitterOf radiation at a givenTemperature T
![Page 54: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/54.jpg)
TEMPERATURE SCALES
Room Temp = 300 K = 27 C = 81 F
Astronomers usually use the Kelvin Scale
K = C + 273 C = (F - 32) x 5/9 ~ (F - 30) / 2 F = (C x 9/5) + 32 ~ C x 2 + 30
![Page 55: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/55.jpg)
The Doppler Effect
• Why does the “pitch” of a police siren differ when, say, a police car is approaching you, or when you are running away from the police (not recommended) ?
• The frequency (the number of sound waves per second) is higher when approaching, and smaller when receding from the source
![Page 56: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/56.jpg)
Doppler Effect in Sound
High Pitch(short waves)
Low Pitch(long waves)
![Page 57: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/57.jpg)
d=1
d=2
d=3
B=1
B=1/9
B=1/4
Brightness decreases inversely as the square of the distance
![Page 58: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/58.jpg)
The Doppler Effect
Velocity c = frequency (f) x wavelength (
![Page 59: Gravity Galileo’s observations on gravity led to Newton’s Law of Gravitation and the three Laws of Motion Objects fall at the same rate regardless of mass](https://reader034.vdocument.in/reader034/viewer/2022051401/56649ec05503460f94bcc376/html5/thumbnails/59.jpg)
Doppler Shift of Wavelengths
• What about the wavelength?• What about light?• Shorter wavelength Blue-shift, • Longer wavelength Red-shift• We can determine the velocity of
astronomical objects, moving away or towards the Earth, by measuring the wavelength of light from the object
• Observed red-shift of galaxies all over the sky shows that galaxies are moving away from one another the Universe is expanding (Hubble’s Law)