B8 Equilibrium, Action, and Reaction

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B-8 Equilibrium, Action, and Reaction

• Lab Answers

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Section 1a Action Reaction
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Section 1b Action Reaction

• 1b The forces acting on the weight, and the
  forces acting on the car, are both zero. This
  means that the forces on each are balance, and
  the system as a whole is balanced.

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Section 1c Action Reaction

• 1c At first, the system has balanced forces. If
  you add more hanging weight, there is now more
  force pulling the weights down. The forces on
  the car are now unbalanced. The weights fall
  down and the car backs up the ramp.

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Section 1d Action Reaction

• 1d At first the system has balanced forces. If
  you remove some hanging weight, there is now less
  force pulling the weights down. The forces on
  the car are now unbalanced. The car moves down
  the ramp, and the weights move upwards.

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Section 1e Action Reaction
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Section 2a Equilibrium at Constant Speed

• Raising the ramp increased the gravity force
  until it exactly balanced the friction force.
  When the force of friction and gravity are equal,
  the car moves at constant speed.

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Section 2b Equilibrium at Constant Speed

• The friction on the car from the ramp surface is
  balanced by a reaction force of the car on the
  ramp.

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Section 3 Using Newtons Third Law on Common
Objects and Activities
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Section 4a What Did You Learn?

• Whenever you (or something else) pushes on
  something, it pushes back on you with equal force.

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Section 4b What Did You Learn?

• You could never bounce or hit a ball because the
  ground or bat or racket wouldnt push back on it.

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Assessment Answer Key 1

• Wave my arms back and forth-forces come in in
  pairs. Forces come in pairs. When I move my
  arms, there will be an equal and opposite force
  that will help push the skateboard

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Assessment Answer Key 1

• Stuff tennis balls in my pockets and throw the
  away from the skateboard. When I throw the
  balls, the balls will exert a force back on me
  and help push the skateboard.

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Assessment Answer Key 2

• The block of lead doesnt fall through the table
  because the table is pushing upward with an equal
  and opposite force of 500 N

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Assessment Answer Key 3a

• I push the cart, and the cart pushes back on me.
  These forces are equal. The frictional force of
  my feet on the ground opposes the push of the
  cart, and I dons move. Because the cart has
  wheels, the frictional force opposing my push on
  the cart is less, and my push overcomes it. The
  cart moves away from me.

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Assessment Answer Key 3b

• I am in equilibrium