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Homework Help: Angular speed of bullet

  1. Sep 6, 2009 #1
    Hey guys,
    I confused about something,please help me.

    I have a bullet and its diameter is 0.5 inches. its speed is 400 foot /sec.
    It makes one complete rotation in the gun 120 mm per turn and length of the gun is 1.5 meter.
    How can I calculate the rotational and angular speed?

    -I used a formula for rotational speed;
    R=2pi.n n=(number of the rotation) which is 1.5 meter/1.2 mm.

    - Angular speed;
    w=v/r w=400 ftsec/0.5inch

    Are my formulas and calculations correct?
  2. jcsd
  3. Sep 6, 2009 #2
    Re: angular speed problem

    wow 1.5 meter is quite a long gun haha. anyway if i am correct 120mm is the distance the bullet travel in one round correct? i would find out how many turns it need to make before it exits the barrel and use the speed that it is traveling. As for the diameter i have no idea what it is for
  4. Sep 6, 2009 #3
    Re: angular speed problem

    Yes u correct 120 mm is the distance the bullet travel in one correct.
    I guess the amount of the turn is 1500/120=12.5
    Given diameter may be for the angular velocity; w=v/r
    But I am not sure about if i can use this diameter for angular velocity.
  5. Sep 6, 2009 #4


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    You are correct. The bullet does 12.5 revolutions inside the gun.

    How many revolutions per second is that? Hint: you need to find how many seconds the bullet spends in the gun.
    How many radians per second is that? That is your ω, the angular speed.
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