Uniformly Accelerated Motion

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Chapter 2

• Uniformly Accelerated Motion

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Speed
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Velocity
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Acceleration
What are the units for acceleration
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Uniformly Accelerated Motion Along a Straight Line

• In this case
• acceleration is a constant
• and the acceleration vector lies in the
  line of the displacement vector.

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The 5 Equations!
(1)
(2)
(3)
(4)
(5)
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Problem Solution Guidelines

• Draw a sketch
• Indicate origin and positive direction
• List the given quantities using the symbols of
  the equations. (si vi a)
• Is time known or do we need to find it
• What are we to solve for
• Write the general equations of kinematics

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More Guidelines

• Rewrite the general equations using the known
  quantities.
• Look at the knowns and unknowns and map a
  strategy of solution.
• Check your units
• Make sure you are answering the question.

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Problem Solution Time

• Fifteen minutes

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Definitions

• Instantaneous Velocity
• the slope of the displacement versus time graph
• Instantaneous Acceleration
• the slope of the velocity versus time graph

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Slopes
Displacement
Time
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Teaming Exercise

• Next Problem solutions

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Free Fall

• The force of gravity points downward
• Acceleration of gravity near the surface of Earth
  is called g 9.8 m/s2 32.1 ft/s2
• Air resistance ignored
• We have then the conditions of one-dimensional
  kinematics straight line motion with constant
  acceleration.

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Sample Problem

• A ball is thrown vertically upward at 10 m/s.
  How high will it get how long will it be in the
  air and how fast will it be moving when it hits
  the ground.

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Projectile Problems Two Dimensional Kinematics

• Ignore air resistance.
• ax 0
• ay g 9.81 m/s2 downward

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The motions in the two directions are independent
Horizontal
Vertical
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Real Motion is the Combination of the Two
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2-D Problem Guidelines

• Set up two 1-D solutions
• Origin x Origin y
• Positive x Positive y
• xi yi
• vxi vyi
• ax 0 ay g

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2-D Guidelines Contd

• Write general kinematic equations for each
  direction
• Rewrite them for the problem at hand
• Find the condition that couples the motions
  (usually time)

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Uniformly Accelerated Motion Along a Straight Line