Propulsion & Recoil

  • Due Oct 13, 2016 at 8:59am
  • Points 2
  • Questions 2
  • Available until Oct 13, 2016 at 8:59am
  • Time Limit None
  • Allowed Attempts Unlimited


Watch the following video tutorial on how the Principle of Action / Reaction applies to propulsion and recoil.

[PDF of Slides]


• Principle of Action / Reaction explains recoil.
• Recoil is the basis for rocket propulsion.
• The two forces of an Action / Reaction pair NEVER balance each other because they always act on different objects or characters!
• Internal propulsion doesn’t work because there are two Action / Reaction pairs; each force in the first pair is balanced by a force in the other Action / Reaction pair. 

Have a question? Go here. 

Optional: Watch this segment from Mythbusters in which they make a rocket using a home water heater:


Optional: Watch this segment from Mythbusters in which they have a fan blowing into a sail:

Note that the Mythbusters use the fan, blowing on the sail, to push the boat side to side, which causes it to "swim" slowly forward. The sail itself is not exerting any force in the forward direction. This is not internal propulsion since the boat is pushing back on the water to swim forward.

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