1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Heisnburg uncertainty

  1. Apr 24, 2009 #1
    1. The problem statement, all variables and given/known data
    A 1.70 kg block rests on the icy surface of a frozen pond, which you can assume to be frictionless. If the location of the block is measured to a precision of 0.30 cm, what is the minimum uncertainty in the block's speed, assuming the mass is known exactly?


    2. Relevant equations
    xp=h/4(3.14)


    3. The attempt at a solution
    xp=h/4(3.14)
    x(mv)=h/4(3.14)
    I plugged in all the values and got v. The answer was wrong. I then multiplies by .0003 and that was also wrong.
     
  2. jcsd
  3. Apr 24, 2009 #2
    potential sources of error # 1:
    0.3 cm = 0.003 meters, not 0.0003 meters


    potential source of error # 2
    they ask you for uncertainty in speed, while the equation for momentum p = mu considers VELOCITY
    an uncertainty in speed of 10m/s , for example, is equal to an uncertainty in velocity of 20 m/s, since a speed up to 10 m/s implies a range of velocities from -10m/s to +10m/s
    so try multiplying the speed by 2 :) (edit: or rather, try dividing the uncertainty in velocity you get by 2 to get the uncertainty in speed, since the block moves in both directions)
     
  4. Apr 24, 2009 #3
    1.03E-32 the velocity by 2 and got 5.16E-33 which is wrong by 10% to 100%.

    I used .003 meters.
     
  5. Apr 24, 2009 #4
    are you sure your math is right? using the version of the heisenberg uncertainty principle that you've provided (there are many variations of it) and the values for m and deltax youve given,
    i get an uncertainty in velocity of 3.24807255 × 10-32
    which is an uncertainty in speed of 1.62403627 × 10-32
     
  6. Apr 24, 2009 #5
    The math is right i did a million times. 1.62E-32 is wrong and it was last my chance. thanks, anways....
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Heisnburg uncertainty
  1. Uncertainty in voltage (Replies: 1)

  2. Atoms, Uncertainty (Replies: 10)

Loading...