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: Acceleration Question 2

  1. Nov 13, 2008 #1
    Could someone please confirm my answer. Thanks

    1. The problem statement, all variables and given/known data

    An electron in a cathode ray tube of a TV set enters a region where it accelerates
    uniformly from a speed of 3.5 × 104 m/s to a speed of 1.4 × 106 m/s in a distance
    of 2.0 cm.
    (a) What is the acceleration of the electron in this region?

    (b) How long is the electron in the region where it accelerates?

    2. Relevant equations

    3. The attempt at a solution

    Given the: initial velocity ---> u = 3.5 x 10^4 m/s
    final velocity -----> v = 1.4 x 10^6 m/s

    distanced traveled S= 2.0 cm --> 2x10^-2 m

    Let acceleration be "a"

    v2-u2= 2as

    a= (v2-u2)/2s = 4.8969375 x 10^9 m/s

    b) let time be "t"

    v = u +at --> t = (v-u)/a = 0.278x 10^-3 s
  2. jcsd
  3. Nov 14, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I'd check your working again. Careful with units as well.
  4. Nov 14, 2008 #3


    User Avatar
    Homework Helper

    Your acceleration is 10,000x off the precise value :tongue2:
    Thus, your time is off by the same magnitude.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook