s ut 12at2 u and a are positive

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s ut 1/2at2u and a are positive
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v u atu is positive and a is negative
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v2 u2 2asu is positive and a is negative
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a-t graph for motion with uniform velocity
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Vertical motion under gravity
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Motion of a free falling object
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• Slope of v-t graph acceleration
• gt g (2.75-0.5)/(30.08)
• 9.375 ms-2

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Q. The experimental value is always smaller than
the actual value, why?

• When the vibrator strikes the ticker tape, it
  produces friction which slows down the falling
  motion.
• The falling motion is slowed down by air
  resistance.

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The coin and feather experiment
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Acceleration due to gravity (g)
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Why does the feather fall down slower than the
coin in air?
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air resistance
fall in air
fall in vacuum
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Air resistance depends on

• Size of the object
• Shape of the object
• Its velocity
• gt parachute

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• A ball is thrown vertically upwards at an initial
  velocity of 100 m s-1.
• What is the acceleration of the ball along the
  time of flight?

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Acceleration always equals to 10 ms-2 pointing
downwards