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

Homework Help: Revolutions of and Electric Drill

  1. Nov 5, 2008 #1

    uno

    User Avatar

    1. A variable speed electric drill motor turning at 100 rev/s is uniformly accelerated at 53.0 rev/s2 up to 210 rev/s. How many turns does it make in the process?



    2. (Accel f - Accel) i x speed



    3. I took 210 - 53 = 157 and multiplied that by 100 and that gave me 15,700 rev. This anser is incorrect. Please advise.
     
  2. jcsd
  3. Nov 5, 2008 #2
    Data we have: Initial angular velocity, acceleration, final angular velocity. We want angular displacement.

    This problem is the rotational analogue of one we would use the for the equation Vf^2 = Vi^2 + 2ax.

    Replace V with angular velocity, a with acceleration and solve for x. Since we are working in units of rev, no division by 2*pi will be necessary - the answer your calculator gives you will be the answer you want.
     
  4. Nov 5, 2008 #3

    uno

    User Avatar

    I got it! Thanks so much for your help.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook