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!

Newtonian - Force, Gravity, and Bungee Jumping

  1. Oct 7, 2009 #1
    1. The problem statement, all variables and given/known data
    A person weighing 55kg jumps off of a bridge with a bungee cord attached. The problem seeks to find the bungee cords Force vector when the acceleration is 7.8m/s2 in the downward direction.

    m = 55kg
    a1 = g = 9.8m/s2

    To find:
    F1 when a2 = 7.8m/s2 downward.

    I've specified my grid as [tex]\uparrow[/tex]+ [tex]\rightarrow[/tex]+ so the accelerations are technically negative.
    2. Relevant equations
    [tex]\Sigma[/tex]F = ma


    3. The attempt at a solution
    [tex]\Sigma[/tex]F = ma
    [tex]\Sigma[/tex]F=55kg(-7.8m/s2)
    [tex]\Sigma[/tex]F = -418N

    [tex]\Sigma[/tex]F = F1 - F2
    [tex]\Sigma[/tex]F = 539N - 418N
    Force of bungee cord acting = +121N
     
  2. jcsd
  3. Oct 7, 2009 #2
    Why did you subtract the forces?
     
  4. Oct 7, 2009 #3
    The 539N was the Force with F=ma and a = g. I think I forgot to write that.
    The -428N was the Force with F=ma and a = 7.8m/s2.

    My inclination was to subtract the forces to get the force required by the bungee cord to slow the decent to the 7.8m/s2
     
  5. Oct 7, 2009 #4
    Well since gravitational force is downwards and he is travelling downwards.......
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Newtonian - Force, Gravity, and Bungee Jumping
  1. Bungee jump (Replies: 5)

  2. Bungee jump (Replies: 1)

  3. The Bungee Jump (Replies: 1)

  4. Bungee Jumping! (Replies: 2)

Loading...