Newton's Laws of Motion

1
Newton's Laws of Motion

• An English mathematician two discovered three
  very important laws for physics
• All ideas had to do with motion

2
Newton's 1st Law of Motion

• Describes motion produced by balanced forces
• An object at rest will remain at rest, and an
  object that is moving at constant speed will
  continue moving unless acted on by an unbalanced
  force

3
Newton's 1st Law

• Also known as the law of inertia
• Inertia an object's resistance to changing its
  state of motion
• Object's don't want to change their motion

4
Newton's 2nd Law

• Describes motion produced by unbalanced forces.
• The net force on an object depends on its mass
  and how fast it is accelerating
• Fma (forcemass x acceleration)

5
Math Practice

• A 52 kg water skier is being pulled by a
  speedboat. The force causes her to accelerate at
  2 m/s. Calculate the force that causes this
  acceleration.

6
More Math Practice

• What mass will a pumpkin have if a force of 450
  Newtons accelerates it to 110 m/s2 ?

7
One more problem

• A squirrel was gathering nuts in a pile. When he
  came back to add to the pile, a seagull was
  eating some of his peanuts. So he threw a .0015
  kg peanut with a force of 15 Newtons at the
  seagull. How fast did the peanut accelerate
  through the air?

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Newtons 3rd Law of Motion

• If you push an object into another object, what
  happens???
• Newtons 3rd Law
• Forces always act in pairs. For every action
  force, there is always an equal and opposite
  reaction force.
• Action force the force that would occur first
• Reaction force the force that takes place
  because of the action force

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Newtons 3rd Law

• Newtons 3rd Law is everywhere!!!
• Give me some examples.
• Birds flying, fish swimming, walking, sitting on
  a chair
• Which is the action force? Which is the reaction
  force?
• Hitting a nail with a hammer
• A bug crashing into a windshield
• Kicking a soccer ball

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Newtons 3rd Law

• Always involves forces acting on two different
  objects!!!