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

I Center of Gravity and Center of Pressure

  1. Jul 24, 2016 #1
    Hello, everyone. This is my first post!

    Center of gravity does not seem like a difficult concept to grasp, but for some reason, I find it difficult to put into words.

    Would I be correct in saying: the center of gravity is a point on an object that represents the average position of an object's mass? This term also takes the distribution of mass into account, and this distinguishes it from the term: center, right?

    Now. Center of pressure. I stumbled upon this concept only after doing some basic web research on rockets. Would I be correct in saying: the center of pressure is a point on an object (a rocket in this case) that represents the average position of aerodynamic drag acting on an object? Of course, taking into account variations in magnitude of aerodynamic drag on the object due to its varying shape and composition.

    I came up with this definition after seeing that the center of pressure of a rocket is near the bottom but above the fins.
    cp_cg_image.gif

    I assume that is the case because the fins induce more drag than the top of the rocket, thus skewing the average position of drag.

    Thank you in advance for any responses!
     
  2. jcsd
  3. Jul 24, 2016 #2

    rcgldr

    User Avatar
    Homework Helper

    Locating center of pressure behind center of mass is for stability, so that a crosswind component causes the rocket to "steer" into the wind to eliminate any cross wind component. The idea is that this corrects for an unintended angle of attack. Wiki article:

    http://en.wikipedia.org/wiki/Static_margin
     
  4. Jul 24, 2016 #3
    So if the rocket is hit from the side by a gust of wind it will rotate around its center of pressure?
    How exactly is it "steering into the wind"?
     
  5. Jul 24, 2016 #4

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    The net force from the lateral wind will be behind the centre of mass. The rocket will rotate about the centre of mass (in addition to being pushed sideways) in such a way as to push the back away from the wind - i.e. tend to point it into the wind.
     
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: Center of Gravity and Center of Pressure
  1. Center of gravity (Replies: 5)

  2. Center of gravity (Replies: 2)

  3. Center of pressure (Replies: 1)

Loading...