Or said another way - how much counterweight does the base of a sign need to keep it from tipping over given a specific max wind?

  • Assume the sign does not let wind through
  • Assume the base of the sign cannot slide on the ground
  • Assume the sign does not flex in the wind
  • Assume total weight of the sign + base is 125 lbs (base is 96 lbs)

Are there any other parameters needed?

The sign has the design and measurements below:

Edit: This would probably be helpful: Width of sign is 8' so the sign is 9' high x 8' wide.


closed as off-topic by Brandon Enright, Kyle Kanos, John Rennie, DavePhD, Prahar Jun 22 '14 at 11:08

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Homework-like questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. See our meta site for more guidance on how to edit your question to make it better" – Brandon Enright, Kyle Kanos, John Rennie, DavePhD, Prahar
If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ By how much wind, do you mean the wind speed required to tip the sign? Also, this problem is not solvable without knowing the drag force the wind exerts on the sign $\endgroup$ – Pranav Hosangadi Jun 21 '14 at 11:02
  • $\begingroup$ Thanks, Pranav. By drag force, is this the same as saying how much wind goes through the sign? Sorry - I'm not up on all the physics terms. Physics class was many decades ago, and I'm just an adult trying to design a marching band prop! :-) In this case, one can assume the sign is completely flat and does not let any wind through it (it's a tarp material). $\endgroup$ – joelq Jun 22 '14 at 1:13
  • $\begingroup$ Oh, and yes, by how much wind, I'm looking for how much wind the sign can take before tipping over. $\endgroup$ – joelq Jun 22 '14 at 1:14
  • You need to calculate where the centroid of the sign is, so assume mass is evenly distributed in base and up the height of the sign.
  • You need to assume aerodynamic force is evenly distributed up the height of the sign.
  • You need to assume a drag coefficient for a flat plate
  • You probably want to assume it is quasi static so it will fall when the aerodynamic force is enough to pivot the sign about the edge of the base.

Free body diagram time!


Not the answer you're looking for? Browse other questions tagged or ask your own question.