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!

How do speed laser guns differentiate between two cars?

  1. May 31, 2015 #1
    If two cars are travelling either in parallel or in close succession to one another how can a laser determine which car it is gauging the speed of?
  2. jcsd
  3. May 31, 2015 #2


    User Avatar
    Science Advisor

    Laser beams are very narrow. When properly used, the operator can tell the cars apart.
  4. May 31, 2015 #3


    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    even more simply, because of their narrow beam, they just aim at the vehicle they want to measure the speed of
  5. May 31, 2015 #4


    User Avatar
    Gold Member

    As has been said, laser guns do not have the problem you seem to think but I believe radar guns do.
  6. Jun 1, 2015 #5


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    It's not clear that laser guns are fault free..

    Perhaps this is relevant..


    I believe the problem of "slippage" is also known as "sliding" and it occurs when the beam slides down the sloping hood/bonnet of the car making it appear to be moving faster than it is. I believe officers are trained to focus the beam on a vertically flat surface like a number plate for this reason.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: How do speed laser guns differentiate between two cars?
  1. Lidar- Laser Guns (Replies: 8)

  2. Red laser guns (Replies: 6)