Newton's second law is mass times acceleration equals force, so a bull that weighs a couple a thousand pounds has more force than some cowboys can hang onto.
"What some people don't know is that the force the bull exerts on the rider is the same as the force the rider exerts back on the bull. The difference is that the bull is about ten times the size of the rider, so that's ten times the acceleration," said UNR physics professor, Ron Phaenuf.
You can gauge the force of one of these bucking bulls, using G's...a gravitational measure.
"A typical roller coaster ride, for example would be up to three G's, which is three times the force of gravity. Extreme ones may be up to five."
Cowboys face even more force than that when they saddle up, tens of G's or even more.
"He has to have very strong biceps to himself on the saddle because if he has somehow gets out, the force he gets when he comes in contact with the bull can be twice as large."
Which is why some cowboys don't always stay on for long.