Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Elementary holicopter question

  1. Jan 29, 2010 #1
    If there's no tail rotor, Will the body of helicopter naturally turn along with the main rotor (in the same direction) or spin toward the opposite direction. Thanks! $15 bet with my friend ><
     
  2. jcsd
  3. Jan 29, 2010 #2

    berkeman

    User Avatar

    Staff: Mentor

    What do you think will happen and why? We have no way to know if this is a homework problem or not. The answer is pretty easy to figure out, and even to demonstrate (without a helicopter).
     
  4. Jan 29, 2010 #3
    My friend think that----
    the engine will turn the helicopter blade in one direction and the body of the helicopter in the opposite direction. The body will not rotate until it has left the ground, because it has friction with the floor. Also the body will spin with a rotational speed proportional to the mass of the body to the blades.


    I think if there's no engine which is no energy input, he may be right. But with continuing energy input, it's not a closed balanced system, energy makes blade spin, then while blade is spinning, the body of helicopter should rotate along with the rotor (same direction).
     
  5. Jan 29, 2010 #4

    DaveC426913

    User Avatar
    Gold Member

    Sorry buddy. Ask your friend if he has a preference of bill denominations that he'd like his reward in.:tongue2:
     
  6. Jan 29, 2010 #5

    berkeman

    User Avatar

    Staff: Mentor

    Agreed.
     
  7. Jan 29, 2010 #6

    DaveC426913

    User Avatar
    Gold Member

    I'll elaborate.

    The engine's torque drives the propellor and the fuselage in opposite directions; the engine does not care which end is the fuselage and which end is the rotor, its purpose is only to rotate its axle relative to its body.


    Try firing up a power drill when its bit is embedded in something. Instead of the drill bit turning clockwise, the whole drill turns counterclockwise, and might twist your arm off.
     
  8. Jan 29, 2010 #7
    In the same direction of course because of friction dragging the heilo body along. I think:confused:
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook