PHYSICS AND LIFE

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PHYSICSAND LIFE
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• 6B (5)
• Lai Kwai Ying

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Content

• What are their relationship?
• Natural phenomena about physics
• Application in our daily life
• Ending

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What are their relationship ?

• In our daily life, there are many examples about
  physics. Also, many scientists discovered the
  physics theory when they are walking, playing and
  so on.Thus, we can see that physics have a close
  relationship between us.
• For example Newton discovered gravity when he
  was sat under a apple tree. Galileo found that
  object of different masses accelerate at the same
  speed under gravity on the Leaning Tower of Pisa.

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Natural phenomena about physics

• Why does the sky appear blue when it is sunny,
  why does it appear red during sunset?
• The short wavelength of light is more easy
  scattering in air particles. Sunshine through
  atmosphere, the colors of blue, green and purple
  which have shorter wavelength are scattering in
  the sky. Thus, the sky is blue in colors in
  daytime.

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• On the other hand, red, orange and yellow have
  longer wavelength, they are difficult scattered.
  Thus, we can see the sky is red and yellow during
  sunset.

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• Why before the water boil, it will produce a
  woo-woo sound?
• It is because the water particles at the bottom
  of the kettle boil first. When they are heated at
  about 100C, they become water vapors and rise.
  However, the water particles above are yet to
  boil.

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• When the vapors are in contract with the water
  particles above, they change back to the water
  droplets immediately. The expansion and
  contraction of water particles bring about
  vibration of water. The upward movement of the
  gas bubbles produce the woo-woo sound.
• On the other hand, once all the water particles
  boil at 100C, the gas bubbles can get to the
  surface stably. No contraction would occur and
  hence no sound will be produce

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Application of our daily life

• The use of speaker
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  A speaker uses electromagnets to transform
  electric current into sound. Electric current and
  magnetic force have a close relationship. When an
  electric current is passed through the wire, a
  magnetic field would be produced.

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• Every time when the current changes its
  direction, the direction of the magnetic field
  produced by the wire round the iron nail also
  changes. Everyone knows that the "Like poles
  repel, unlike poles attract" principle applies to
  magnetic force. The magnetic pole of the coil
  keeps on alternating, sometimes attracting the
  permanent magnet and sometimes repelling it.
• Attach a diaphragm to the coil. When they vibrate
  together, the surrounding air would be mobilized.
  Isn't vibration of air sound? This is the
  operation of a speaker.

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• A lightning rod
• A lightning rod is not used to block lightning,
  but to provide a safe path for the charges in the
  cloud to neutralize with those on the ground,
  thus it could protect the building from being
  damaged by lightning.

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• According to a principle in electrostatics,
  charge density is higher at the sharper edges of
  the conductors. Therefore, more positive charges
  are gathered at the tip of the lightning rod,
  causing the negative charges in the clouds to
  frequently travel along the rod and discharge on
  the ground. This prevents excessive negative
  charges to accumulate in the clouds or else,
  once they discharge, the very powerful lightning
  would strike those buildings with more positive
  charges.

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Ending

• From this project, L can know that the physics
  world is unlimited. In fact, these examples are
  only a small part in our life, we need continue
  to explore the physics world.
• It is funny!

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• The End