Gravitational acceleration

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Gravitational acceleration
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Lets practice using the kinematics equations

• Just for fun!

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Problem

• A soccer player, running at a speed of 2.6 m/s,
  decides to accelerate. For the next 18 m, he
  speeds up with an acceleration of 0.45 m/s/s.
  What is his speed at the end of the run?

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Recall

• Variables
• ?x a vf vo ?t
• vf vo a ?t ? ? ? ?
• ?x 1/2 (vo vf) ?t ? ? ? ?
• ?x vo ?t 1/2 a ?t2 ? ? ?
  ?
• vf2 vo2 2a?x ? ? ? ?

On page 38 of your text.
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Problem

• The length of the barrel of a primitive blowgun
  is 1.6 m. Upon leaving the barrel, a dart has a
  speed of 24 m/s. Assuming the dart is uniformly
  accelerated, how long does it take for the dart
  to travel the length of the barrel?

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Recall

• Variables
• ?x a vf vo ?t
• vf vo a ?t ? ? ? ?
• ?x 1/2 (vo vf) ?t ? ? ? ?
• ?x vo ?t 1/2 a ?t2 ? ? ?
  ?
• vf2 vo2 2a?x ? ? ? ?

On page 38 of your text.
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Which vector represents the skiers acceleration
at the instant shown?
A
B
C
D
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When do we use g?

• When does something have an acceleration of 10
  m/s/s down?
• Always use the operational definition.
• Everything has an acceleration 10 m/s/s IF it is
  falling off the physics building in a vacuum.
• Let g stand for 10 m/s/s.

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Which falls faster, a big rock or a small rock?
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The ball and the feather
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A short thought experiment
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A short thought experiment
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A short thought experiment
GLUE
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Cliff Diving
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Cliff Diving
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Check Question
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Problem

• You and a friend stand on the edge of a 40 m
  cliff. You throw a red ball straight up at 30
  m/s. At the same time, your friend throws a blue
  ball straight down at the same speed.
• Compare the velocities of the two balls right
  before they hit the ground.
• How much later does the red ball hit than the
  blue ball?

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0 m/s
10 m/s
20 m/s
30 m/s
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0 m/s
3 sec
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0 m/s
3 sec
30 m/s