Saturday, November 30, 2013

How Hard Does a Giraffe Hit?

While watching t.v. I stumbled across a show about giraffes, and was particularly interested on the segment about male giraffes fighting each other. If you've never seen it before there's a video above (watch out for the music). Basically a giraffe swings its head into the other giraffe using its neck to snap its head around. I saw this and wondered how hard that giraffe head is hitting. Giraffes necks average about six feet long, and when they swing their heads they use about half of their necks, making an arc with a radius of about one meter. The swing is about 120 degrees, and takes about one third of a second. I also am assuming a giraffes head to weigh about 100 pounds. Using the equation relating angular acceleration, change in angle, time, and initial angular velocity, I determined the acceleration of the giraffe's head to be about 37.7 rad/s*s. That combined with the weight of the giraffes head gives a force of about 1710 N. Would that be enough to break bones?
Assuming giraffe's land blows with their horns, properly called ossicones and having a surface area of about .01621m (2 4in diameter ossicones), the blow would hit at about 7*10^6 N/m*m.  According to the table provided in the text book, this is not enough force to break limb bones (170*10^6 N/m*m), but it is close, a reasonably harder hit could potentially break bones.