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: Velocity and acc question

  1. Sep 15, 2011 #1
    How is V(initial) = 0 when Acc at start is equal to 4m/s^2

    shouldnt there be some type of Velocity?

    Attached Files:

  2. jcsd
  3. Sep 15, 2011 #2

    Lets say you drop a ball from your hand. The acceleration is 9.8m/s^s downward, but when the ball is in your hand it is not moving. (unless of course you are swinging your arm).

    So at initial, the very beginning, there is no velocity. Velocity changes due to acceleration.
  4. Sep 15, 2011 #3
    I thought this was only true for "free falling" objects....

    For example.... I posted some graphs...
    graph 1 is velocity increasing... then graph 2 is acceleration based off graph 1....

    However if velocity had a constant slope say y = 3.. then acc would be zero...
    My thoughts where... if initial acceleration is not zero in word problem then initial velocity must not be zero... which i showed in my two graphs...
    Obviously I am wrong.. I just need to wrap my mind around it ..

    Attached Files:

    • gra.JPG
      File size:
      3.8 KB
  5. Sep 15, 2011 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Acceleration is a change in velocity during some time interval. In order for any object to begin moving from rest, whatever the direction of travel, the object must undergo acceleration.

    When you are in a car stopped at a traffic light, and the car takes off after the light changes, the force you feel pushing you into the seat back is due to the car accelerating away from the traffic light.
  6. Sep 15, 2011 #5
    Thank you..
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook