Chap' 5 Force and Motion

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Chap. 5 Force and Motion

• Force vectors

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A Short Catalog of Forces

• Weight
• Spring Force
• Tension Force
• Normal Force
• Friction
• Drag (resistive force )
• Thrust

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Stop to think 5.1 P 129Stop to think 5.2 P
134Stop to think 5.3 P 137Stop to think 5.4 P
139Stop to think 5.5 P 145

• Example 5.4 P143
• Example 5.5 P144
• Example 5.6 P144

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Identifying Forces and Free-body Diagram
A skier is pulled up a hill
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An elevator accelerates upward
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Mass

• An objective mass is a measure of the amount of
  matter it contains.
• Inertial mass

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Newtons second law

• In the form
• Units of Force 1N 1 Kgm/s2

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Newtons First Law

• Newtons first law Law of inertial
• An object that is at rest will remain at rest,
  or
• an object that is moving will continue to move
• in a straight line with constant velocity,
• if the net force acting on the object is zero.
• The object is at rest. This is static
  equilibrium.
• The object is moving in a straight line with
  constant velocity. This is dynamic equilibrium

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Newtons third law

• If one object is exerting a force on a second
  object, then the second object is also exerting a
  force back on the first object. The two forces
  have exactly the same magnitude but act in
  opposite directions.

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Free body Diagram

• Identify all forces acting on the object.
• Draw a coordinate system
• Represent the object as a dot at the origin of
  the coordinate axes.
• Draw vectors representing each of the identified
  forces
• Draw and label the net force vector Fnet

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A hockey puck slows down as it hits a rough patch
of ice.