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  • Common Questions Asked in Post UTME Physics Exams. Day3


    Chima Sunday (Tutor)
    15-06-2016 13:57:00 +0000

    Try your best to solve these questions. Show working on paper when necessary and include a picture of your hand written Solution in your response. Wish you the best!

    1. Which of the following serves as a nuclear moderator in a nuclear reactor
    A. Cadmium rod
    B. Boron rods
    C. Aluminium rods
    D. Heavy water

    Updated Solution
    A nuclear reactor is a device that utilizes nuclear reactions via fusion or fission reaction to generate electricity.
    Moderating a nuclear reactor is a process whereby a fast moving neutron usually used in striking the fuel is slowed down, in which when there is head on collision with the neutron, extract some of the kinetic energy possessed by the neutron and consequently slowed its velocity. Examples of such moderators are Heavy water(they are water formed with deuterium), graphite rods etc

    2. The half life of a radioisotope is 92 seconds, The N/No left after 2 hours is
    A 54.22
    B. 0.368
    C. 650.59
    D. 3.0×10-24

    Updated Solution
    Here they are actually asking us to find the fraction of the left over(i.e N/No) after 2 hours, if the radioisotope has a half life of 92 seconds. there are actually two ways of doing this, but i am going to use one such ways and state the second one for you to try and use. Although the first method is a consequence of the second
    recall that N/No = (1/2)t/T
    where T = half life = 92sec. and t = 2 * 60 * 60 = 2 * 3600sec
    so N/No = (1/2)2*3600/92
    this can be approximated to be = (0.5)78 = 3.3*10-24
    So correct Option is D
    is by using the formular i.e N/No = e-λt
    where λ = 0.693/T

    2 8 0

  • Shegx01

    question 1 is d(heavy water) or by using graphite to show down nuclear reaction

    2 15-06-2016 14:57:00 +0000

  • Shegx01

    question 2 not clear enough sir or I can't comprehend

    2 15-06-2016 14:59:00 +0000

  • armsy mohd

    question 2. is 92sec x 60secs x 2hour / 69hrs/secs = 54.22

    2 15-06-2016 15:37:00 +0000

  • Shegx01

    uniben is now live they are doing post utme CBT

    2 15-06-2016 15:38:00 +0000

  • Chima Sunday (Tutor)

    Thanks to all of that attempted to solve this question, that was a huge bold step keep it up. Also do know that this post has been updated with their detailed solutions, so try and check it up.

    2 17-06-2016 15:25:00 +0000

  • OAA Oke

    pls sir use the other method to solve number 2 que it looks confusing

    2 17-06-2016 16:43:00 +0000

  • armsy mohd

    thank you for the soln after being tried. we count on Ur support in this tutorials. God bless u.

    2 17-06-2016 17:25:00 +0000

  • Chima Sunday (Tutor)

    @OAA, recall that lin2 = log2 base e = 0.693, and recall from log that e^log a base e = a
    so i think if you use this hint correctly you will fall back to the first method we applied. Thanks for your interest

    2 27-06-2016 11:43:00 +0000