10/3/11 1 Newton’s Laws of Motion #1: A body continues at rest or in uniform motion in a straight line unless acted upon by a force. Why doesn’t the soccer ball move on its own? What causes a soccer ball to roll to a stop on the grass? Newton’s Laws of Motion #2: The amount of change in a body’s motion is proportional to the force acting on it, and along the same direction as the force. F (force) = m (mass) × a (acceleration) If I kick the ball this way It will move in the same direction If I kick the ball harder, It will go faster The more massive the body, the more force you need to change its motion Need a lot of force to move a bowling ball Only need a little force to move a ping- pong ball Newton’s Laws of Motion #3: When one body exerts a force on a second body, the second body exerts an equal and opposite force back on the first body. What’s happening at the moment when I kick the soccer ball? Hint: Think about what would happen if you kicked the ball really hard with no shoes on. Gravity Lecture Tutorial: Pages 29-31 • Work with a partner or two • Read directions and answer all questions carefully. Take time to understand it now! • Come to a consensus answer you all agree on before moving on to the next question. • If you get stuck, ask another group for help. • If you get really stuck, raise your hand and I will come around. The Moon and Earth pull on each other with equal strength and in opposite directions Earth Moon F g F g
Transcript
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Newton’s Laws of Motion #1: A body continues at rest or in uniform motion in a
straight line unless acted upon by a force. Why doesn’t the soccer ball move on its own? What causes a soccer ball to roll to a stop on the grass?
Newton’s Laws of Motion #2: The amount of change in a body’s motion is
proportional to the force acting on it, and along the same direction as the force.
F (force) = m (mass) × a (acceleration)
If I kick the ball this way
It will move in the same direction
If I kick the ball harder,
It will go faster
The more massive the body, the more force you need to
change its motion
Need a lot of force to move a bowling ball
Only need a little force to move a ping-pong ball
Newton’s Laws of Motion
#3: When one body exerts a force on a second body, the second body exerts an equal and opposite force back on the first body.
What’s happening at the moment
when I kick the soccer ball?
Hint: Think about what would happen if you kicked the ball really hard with no shoes on.
Gravity Lecture Tutorial: Pages 29-31
• Work with a partner or two • Read directions and answer all questions carefully.
Take time to understand it now! • Come to a consensus answer you all agree on before
moving on to the next question. • If you get stuck, ask another group for help. • If you get really stuck, raise your hand and I will
come around.
The Moon and Earth pull on each other with equal strength
and in opposite directions
Earth
Moon
Fg Fg
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You and Earth pull on each other with equal strength and
in opposite directions
Earth
Fg
Fg
The more massive the body, the more force you need to change its motion
Earth
Fg
Fg
Which one will move more: You or Earth?
a (acceleration) = F (force) m (mass)
Light and Matter: Reading Messages from the
Cosmos How do we experience light?
• The warmth of sunlight tells us that light is a form of energy
• We can measure the power, or flow of energy over time, of light in units of watts
• One watt is about the amount of power used to lift an apple over your head in 1 second
Colors of Light
• White light is made up of many different colors
How do light and matter interact?
• Emission • Absorption • Transmission
– Transparent objects let light through – Opaque objects block or absorb light
• Reflection or Scattering
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Reflection and Scattering
Mirror reflects light in a particular direction
Movie screen scatters light in all directions
What is light?
• Light can act either like a wave or like a particle
• Particles of light are called photons
Properties of Waves
• Wavelength is the distance between two wave peaks
• Frequency is the number of times per second that a wave vibrates up and down
wave speed = wavelength x frequency
Light: Electromagnetic Waves
• A light wave is a vibration of electric and magnetic fields
• Light interacts with charged particles through these electric and magnetic fields
Wavelength and Frequency
wavelength x frequency = speed of light = constant
Particles of Light
• Particles of light are called photons • Each photon has a wavelength and a
frequency • The energy of a photon depends on its
frequency
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Wavelength, Frequency, and Energy
λ x f = c λ = wavelength , f = frequency c = 3.00 x 108 m/s = speed of light
E = h x f = photon energy
h = 6.626 x 10-34 joule x s = Plank’s constant
What is the electromagnetic spectrum?
The entire possible range of wavelengths or frequencies light
can have
What is the electromagnetic spectrum? Gamma Rays • Very high frequency
• Very high energy
• Damaging to humans!
-The atmosphere takes care of us…
• Can only be studied from space
• Gamma ray bursts, nuclear reactions
X-rays
• Still pretty high energy
• Not as bad as gamma rays, too much is still bad
• Medical uses
• Can still only be studied from space
• Gas in galaxy clusters, supernova remnants, or the Sun’s corona
Ultraviolet (UV) Light
• Getting closer to visible light!
• Too much is still a bad thing (wear sun block…)
• Visible in supernova remnants and coming from very hot stars
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Visible Light
• Light our eyes can see!
• Wavelengths about as long as bacteria
• About 400-700 nanometers
• Produced in stars
Infrared (IR) Light • We glow in IR light!
• Beyond the range of human sight
• Night-vision goggles
• Given off by planets, some gas clouds, and moons
Radio • Very wide range of wavelengths / frequencies
• Subcategories: TV, AM & FM radio, RADAR, microwaves
• The CMB (cosmic microwave background) glows in microwaves
EM Spectrum Lecture Tutorial: Pages 45-47
• Work with a partner or two • Read directions and answer all questions carefully.
Take time to understand it now! • Come to a consensus answer you all agree on before
moving on to the next question. • If you get stuck, ask another group for help. • If you get really stuck, raise your hand and I will
come around.
Telescopes & Light
• Telescopes gather information from the entire EM spectrum
• Why do some objects glow in IR light? Why do some give off x-rays?
• Interactions between light & matter
Properties of Matter • Structure of matter • Phases of matter • How energy is stored in atoms
How do light and matter interact?
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What is the structure of matter?
Atom Nucleus
Electron Cloud
Atomic Terminology • Atomic Number = # of protons in nucleus • Atomic Mass Number = # of protons + neutrons
• Molecules: consist of two or more atoms (H2O, CO2)
Atomic Terminology • Isotope: same # of protons but different # of
