Action reaction force quick question

  1. Jun 16, 2012 #1
    1. The problem statement, all variables and given/known dataA firewoman opens the fire hose, and water sprays forward. What is the action force and reaction force?

    2. Relevant equationsnone

    3. The attempt at a solution
    I was thinking that the action force would be water pushing on air and reaction air pushing on water? But how would this be possible in space where there is a vacuum?
  2. jcsd
  3. Jun 16, 2012 #2


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    I think the question is rather ambiguous. The firewoman exerts a force on the hose to hold it at rest. There will be a corresponding reaction force. Can you describe this reaction force?

    Also, the hose will exert a force on the water. What is the reaction force to this?

    As you stated, the water will exert a force on the air as it moves through the air. And you correctly stated that the reaction force would be the air exerting a force on the water.

    [By the way, when dealing with action-reaction pairs, it doesn't matter which of the two forces you call the "action" force and which the "reaction" force.]

    If the hose and firewoman are in a vacuum, then of course there would be no force of the water on any air. But you would still have the other action-reaction pairs mentioned above.
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