1. Not finding help here? Sign up for a free 30min 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!

Two physics questions

  1. Nov 8, 2007 #1
    1. The problem statement, all variables and given/known data

    Which of the following is not a unit of velocity?
    A) m/s C) km/ms
    B) m/N D) mm/ms

    If an object starts from rest and travels a distance d in t sec, which of the following equations may be used to find its acceleration?
    A) Vf = Vi + at C) d = Vi t + ½ at2
    B) Vf2 = Vi2 +2ad D) d = ½ (Vf + Vi) t

    2. Relevant equations

    In problems

    3. The attempt at a solution
    Ok, for #1 I am going or answer B because I have never seen that before.

    FOr the 2nd one, I amgoing to go with A.

    AmI right?
  2. jcsd
  3. Nov 8, 2007 #2
    Only A is a unit of velocity.

  4. Nov 8, 2007 #3

    Shooting Star

    User Avatar
    Homework Helper

    Use some logic.

    1. Velocity has dimension of distance/time. Which of them does not ultimately decompose into that?

    2. Choice A doesn't even have 'd' in it. Which one has d and t and the initial velocity?
  5. Nov 8, 2007 #4
    kilometers per millisecond and mmillimeters per millisecond may be very unusual units of velocity (more properly speed since direction is unstated) but they are units of speed.
  6. Nov 8, 2007 #5
    Damn, im sorry.


    So #1 is B

    and # 2 is C

  7. Nov 8, 2007 #6

    Shooting Star

    User Avatar
    Homework Helper

    That's more like it!
  8. Nov 8, 2007 #7
    C. Using one of the three laws of projectile motion.

    It obviously cant be A as it doesn't have Distance in it. It can't be B because that doesn't have time in it and D doesn't even hold acceleration.

    Therefore C is the right answer you would just need to re-arrange the equation to get a as a subject.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?