Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Difference between these equations?

  1. Nov 20, 2013 #1

    Zondrina

    User Avatar
    Homework Helper

    I've been curious about this for awhile. What's the difference between the following two equations:

    ##(1) v_2 = v_1 + a \Delta t##

    ##(2) v_2^2 = v_1^2 + 2a \Delta d##

    My hunch is that ##(1)## represents the final speed in a non-parabolic scenario while ##(2)## is used when the object travels in an arc.

    I was curious about this because the two equations wont produce the same answer when asked to find the "final velocity" of an object.
     
  2. jcsd
  3. Nov 20, 2013 #2

    adjacent

    User Avatar
    Gold Member

    2 is used when an object travels in a straight line.Let's put it this way
    ##v=u+at##
    ##v^2=u^2+2as## (v= final velocity,u = initial velocity)
    First equation is just a rearrange of acceleration equation which is
    ##a=\frac{v-u}{t}##
    The second equation is formed by combining the equations
    ##s=\frac{1}{2}(u+v)t## and ##v=u+at## (First equation)
    These equations are known as Equations of motion.
    Each equation has one quantity absent,in equation 1,it's s
    In equation 2,It's t.

    Yes,the two equations looks similar,because it's subject is v.However,two equations have different quantities.

    If for example,u= 0. v= 10m/s .a= 2
    Then time taken is 5 sec
    and distance traveled is 25m.
    What's the problem in this?Does this look similar?Does distance and time look similar?


    Note:s is displacement,v and u is velocity.They are not distance and speed
    All the equations of motion applies if acceleration is uniform and object move in a straight line
     
    Last edited: Nov 20, 2013
  4. Nov 20, 2013 #3
    But they do produce the same answer and they both apply to uniformly accelerated motion.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook