Fundamental Forces of the Universe

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Fundamental Forces of the Universe
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There are four fundamental forces, or
interactions in nature.

• Strong nuclear
• Electromagnetic
• Weak nuclear
• Gravitational

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Strong nuclear force

• Holds the nuclei of atoms together
• Very strong, but only over very, very, very short
  distances (within the nucleus of the atom)

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Electromagnetic force

• Causes electric and magnetic effects
• Like charges repel each other
• Opposite charges attract each other
• Interactions between magnets
• Weaker than the strong nuclear force
• Acts over a much longer distance range than the
  strong nuclear force

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Weak nuclear force

• Responsible for nuclear decay
• Weak and has a very short distance range

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Gravitational force

• Weakest of all fundamental forces, but acts over
  very long distances
• Always attractive
• Acts between any two pieces of matter in the
  universe
• Very important in explaining the structure of the
  universe

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Remember

• The weak nuclear force is NOT the weakest of the
  fundamental forces.
• GRAVITY is the weakest force, but most important
  in understanding how objects in the universe
  interact.

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Nuclear Reactions

• There are two kinds of nuclear reactions
• Fusion
• Fission
• Protons and neutrons are the two most important
  subatomic particles in the nucleus and
  participate in these reactions.

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Fusion

• Fusion is the process of combining nuclei of
  atoms to make different atoms.
• This reaction is going from SMALL to LARGE
  particles.
• Think of fusing two things together.

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Fusion

• Nuclear fusion happens at the sun.
• One isotope of hydrogen-3 and one isotope of
  hydrogen-2 combine to form a helium atom, a
  neutron and lots of energy!!!

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Fusion

• Where does the energy come from?
• Energy is gained when the two hydrogen atoms
  break apart.
• Some of this energy is used up to create the
  helium atom, but the rest is given off as light.
• Mass is converted to energy!
• E mc2 (c 3.0 X 108 m/s) ? Speed of light
• Since the speed of light is so large even a small
  mass will be converted to a very large energy.

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About Nuclear Fusion

• Nuclear Fusion is the energy source of the
  future.
• It is what provides the sun and stars large
  amounts of energy for billions of years.
• We have been able to use fusion on earth to make
  nuclear bombs but have not been able to make it a
  sustainable energy source.
• If we were able to make fusion a sustainable
  energy source one teaspoon of fusion fuel (heavy
  hydrogen) could produce more than 20 tons of
  coal.
• One ton is 2,000 lbs and roughly 250 gallons of
  oil so 20 tons would be approximately 5,000
  gallons of oil! That would fill up my tank 333
  times!

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Fission

• Fission is the process of breaking up the nucleus
  of an atom.
• This reaction is going from LARGE to SMALL
  particles.
• Think of breaking two things apart.

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Fission

• Nuclear fission begins when a neutron hits the
  nucleus of large atom.
• Adding this neutron makes the nucleus unstable
  and it splits into two smaller nuclei and two
  neutrons.

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Fission
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About Nuclear Fission

• Nuclear Fission happens on earth at Nuclear Power
  Plants.
• This type of energy also made the atomic bombs
  that destroyed Hiroshima and Nagasaki in World
  War II.
• Fission occurs with a radioactive, unstable
  material such as Uranium or Plutonium whose atoms
  nucleus is ready to fall apart at the slightest
  nudge and releases large amounts of energy and
  extra neutrons.

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Fission Examples
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More about Fission

• The energy released is called radiation. The
  radioactive energy released from Plutonium can
  damage human cells. This can happen slowly
  naturally (with both Uranium and Plutonium)- but
  when it is combined with TNT (Trinitrotoluene)
  the Plutonium reaction compresses and becomes
  very dense.
• The extra neutrons that are released bump into
  more Plutonium and a chain reaction occurs. The
  extra energy is released all at once causing
  disastrous consequences.

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Video About Hiroshima and Nagasaki
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Chain Reactions

• If there are other 235U atoms nearby, the
  neutrons that came from splitting the first 235U
  nucleus can hit other atoms.
• The nuclei of these other atoms will release more
  neutrons and split more 235U atoms.
• This is called a chain reaction.

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Chain Reactions
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How Nuclear Power Plants Use Fission

• Nuclear Power Plants use Uranium because it
  naturally undergoes fission slowly making it
  easier to induce fission at power plants.
• Pros- One pound of Uranium produces energy equal
  to about a million gallons of gasoline.
• It allows us to become less dependent on fossil
  fuels and Nuclear Energy is sustainable.
• Cons- Radioactive waste and transporting the fuel
  can be dangerous.
• If not operated properly, disasters like
  Chernobyl Power Plant (1986) accident could
  occur. This accident released 50 tons of
  radioactive waste, contaminated millions of acres
  of land, and at least a 1,000 people died from
  health conditions from exposure to the
  radioactive material.

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Chernobyl Disaster
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Radioactivity

• Radioactivity is the process where the nucleus
  emits particles or energy. It is the release of
  energy.
• There are three types of radioactive decay
• Alpha decay
• Beta decay
• Gamma decay

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Alpha decay

• The reason alpha decay occurs is because the
  nucleus has too many protons which cause
  excessive repulsion. In an attempt to reduce the
  repulsion, a Helium nucleus is emitted so that
  the nucleus of an atom can feel stable.
• A particle with 2 protons and 2 neutrons (Helium
  atom) is released from an unstable nucleus.
• Alpha decay can be stopped by clothing, skin, a
  few centimeters of air, or cardboard.

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Alpha Decay Example
After Decay Stable Nucleus
Before Decay Unstable Nucleus
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Beta decay

• Beta decay occurs when the neutron to proton
  ratio is too great in the nucleus and causes
  instability.
• This occurs when a neutron of an instable nucleus
  of a radioactive isotope splits into a proton and
  an electron.
• The electron is emitted.
• Beta decay can be stopped by dense clothing or
  wood.

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Beta Decay Example
BlueNeutron
RedProton
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Gamma decay

• Gamma decay occurs because the nucleus is at too
  high an energy. The nucleus falls down to a lower
  energy state and, in the process, emits a high
  energy photon known as a gamma particle.
• This involves the release of high-energy,
  electromagnetic radiation from the nucleus of the
  atom.
• Gamma rays have even more energy than X-rays.
• It can only be stopped with thick walls of
  concrete or lead.

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Gamma Decay Example
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Radioactive Decay
Alpha Decay Beta Decay Gamma Decay
of Protons
of Neutrons
What is released?
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Radioactive Decay
Alpha Decay Beta Decay Gamma Decay
of Protons Decreases by 2 Increases by 1 unchanged
of Neutrons Decreases by 2 Decreases by 1 unchanged
What is released? An alpha particle An electron and energy A gamma ray (high energy)
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Half-Life
Time (years) Fraction of element left Amount left (g) Half-life
0 1 80 0
1000 1/2 40 1
2000 1/4 20 2
3000 1/8 10 3
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Half-Life

• The half-life of a radioactive element is the
  TIME it takes for HALF of the radioactive atoms
  to decay to stable ones.
• If there are 80 grams of a radioactive element
  that has a half-life of 1000 years, then after
  1000 years half of the element, or 40 grams of
  the element, will remain.
• Now that there are only 40 grams left, how many
  grams will be left after another 1000 years has
  passed?
• There will be only 20 grams remaining.

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Half-Life

• The number of half-lives that occur for an
  element is found by dividing the total time by
  the half-life of a radioactive element.
• Total Time Half Life of half-lives
• An element has a half-life of 1000 years. How
  many half-lives have occurred after 2000 years
  has passed?
• Two half-lives because 2000 years 1000 years
  2

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Half-Life

• To find the fraction of the original amount think
  of the original amount as 1 and then divide by 2.
• 1 2 1/2, one-half is how much remains after
  one half-life occurs.
• If two half-lives occur then divide the original
  amount by 2 twice.
• 1 (22) 1 4 1/4, one-fourth is how much
  remains after two half-lives occur.
• What do you do if three half-lives occur?
• 1 (222) 1 8 1/8, one-eighth is how much
  remains after three half-lives occur.

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Half-Life Practice Problem 1

• The radioactive isotope Fluorine-11 has a
  half-life of 11.0 s. How many half-lives occur
  in 11.0 s for Fluorine-11?
• Only one half-life occurs because the half-life
  of Fluorine-11 is 11.0 s.
• If you started with 30 g, how many grams are left
  after 11.0 s?
• Since one half life occurs, 30 g is divided by 2
  and there are 15 g left.
• What fraction of the original amount is left?
• One-half of the original amount is left.

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Half-Life Practice Problem 2

• The radioactive isotope Carbon-15 decays very
  fast and has a half-life of 2.5 s. How many
  half-lives occur in 5.0 s for Carbon-15?
• Two half-lives occur because 5.0 s 2.5 s 2.
• If you started with 100 g, how many grams are
  left after 5.0 s?
• Since 2 half-lives occur, the 100 g must be
  divided by 2 twice 100 g 4 25 g.
• What fraction of the original amount is left?
• 1 (22) 1 4 1/4, one-fourth remains.

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Half-Life Practice Problem 3

• Neon-15 has a half-life of 30 s. How many
  half-lives occur in 1.5 min?
• Three half-lives occur because 1.5 min 90 s and
  90 s 30 s 3.
• If you started with 56 g, how many grams are left
  after 1.5 min?
• Since 3 half-lives occurred, the 56 g must be
  divided by 2 three times 56 g 8 7 g.
• What fraction of the original amount is left?
• 1 (222) 1 8 1/8, one-eighth is left

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1. The strongest of the four fundamental forces?

1. Strong nuclear
2. Weak nuclear
3. Gravity
4. electromagnetic

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2. Gravity depends on two thingsone is distance
the other is

1. Inertia
2. Orbits
3. Mass
4. Volume

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3. This type of force that holds the nuclei of
atoms together

1. electromagnetic
2. Weak nuclear
3. gravitational
4. Strong nuclear

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4. This is the force where opposite charges
attract

1. Strong nuclear
2. Weak nuclear
3. Gravitational
4. Electromagnetic

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5.If an element is radioactive it means that its
nucleus is _______.

1. small
2. unstable
3. large
4. stable

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6. This is the type of decay that is the weakest
and two protons and two neutrons are released.

1. alpha
2. beta
3. gamma
4. fusion

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7. What is the force that is responsible for
nuclear decay?

• A. Electromagetic
• B. Strong nuclear
• C. Gravitational
• D. Weak nuclear

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8. This type of reaction goes from large to small
and breaks up a big atom into smaller atoms.

1. beta
2. fusion
3. alpha
4. fission

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9. The half-life for Krista-26 is 4.5 years. If
the initial amount is 1500 g. how much will be
left after 4 half-lives.

1. 187.5
2. 46.88
3. 93.75
4. 102.32

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10. As the distance between objects increase the
gravity

1. increases
2. decreases
3. Stays the same

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11. The more mass an object has

1. The closer an object is to another object
2. The less gravity it has acting on it
3. The more gravity is acting on it

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12. Where does nuclear fission take place?

1. Earth
2. Sun
3. Moon

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13.This type of decay is the strongest and
releases a photon

1. alpha
2. beta
3. gamma
4. fusion

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14. After 4 half-lives a radioactive substance
will have only about..?

1. 1/8
2. 1/16
3. 1/2
4. 1/32

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15. Paper clips attracted to a piece of metal is
an example of what type of force

1. Weak nuclear
2. Strong nuclear
3. Gravity
4. electromagnetic

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16. When multiple nuclear fissions occur it is
called?

1. Nuclear fission
2. Chain reaction
3. Nuclear fusion
4. Dominos

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17. This is the process where the nucleus of an
atom releases particles or energy.

1. fusion
2. fission
3. decay
4. Radioactive decay

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18.A 560 g sample of Webb-42 decays to 140 ghow
many half-lives have passed?

1. 1
2. 4
3. 3
4. 2

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19. What force makes it difficult for me to dunk
a basketball?

1. Weak nuclear
2. Strong nuclear
3. Gravity
4. electromagnetic

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20. How many neutrons are lost during gamma decay?

1. 1
2. 2
3. 4
4. 0