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!

Questions about the formula for acceleration

  1. Sep 25, 2014 #1
    1. The problem statement, all variables and given/known data


    I know that acceleration = change in velocity/change in time. Wouldn’t acceleration therefore also = distance/time2?

    I thought this was true until i learned the formula for motion
    s=ut*1/2at2
    where
    s = distance and u = initial velocity

    Here, if you re-arrange the formula (and assuming that initial velocity =0), a= 2s/t2

    So which of these formulas are right?

    And if i were to create a graph where the slope can help find the acceleration, should i graph 2*distance vs t2 or just distance vs t2?
     
  2. jcsd
  3. Sep 25, 2014 #2

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Average acceleration is ##\Delta v / \Delta t##, and average velocity is ##\Delta s / \Delta t##. But ##\Delta v## is not average velocity, so you cannot combine those two equations.
    The SUVAT formula you quote is only valid for constant acceleration.
     
    Last edited: Sep 25, 2014
  4. Sep 25, 2014 #3

    rcgldr

    User Avatar
    Homework Helper

    Assume constant acceleration, using va for v average:

    v1 = v0 + a Δt
    va = 1/2 (v0 + v1)
    s1 = s0 + va Δt = s0 + 1/2 (v0 + v1) Δt = s0 + 1/2 (v0 + (v0 + a Δt)) Δt = s0 + v0 Δt + 1/2 a Δt^2
     
  5. Sep 25, 2014 #4
    Acceleration IS equal to distance/time2

    distance = meters (or m)
    time = seconds (s)

    The units for acceleration is: m/s2
     
  6. Sep 25, 2014 #5
    No, the fact that is has the same units does not mean that they are the same.
    Work is not torque even though both are measured in N*m.

    Acceleration is a measure of change in speed. If the speed is constant, you have no acceleration even if there is some distance traveled in some time.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Questions about the formula for acceleration
Loading...