A common example of a screw is the wrench associated with a force acting on a rigid body. Let P be the point of application of the force F and let P be the vector locating this point in a fixed frame. The wrench W=(F, P×F) is a screw. The resultant force and moment obtained from all the forces Fi i=1,...,n, acting on a rigid body is simply the sum of the individual wrenches Wi, that is
Notice that the case of two equal but opposite forces F and -F acting at points A and B respectively, yields the resultant
This shows that screws of the form
can be interpreted as pure moments.
Read more about this topic: Screw Theory
Famous quotes containing the word wrench:
“I believe we are still so innocent. The species are still so innocent that a person who is apt to be murdered believes that the murderer, just before he puts the final wrench on his throat, will have enough compassion to give him one sweet cup of water.”
—Maya Angelou (b. 1928)
“That is what we must make people feel... the catch in the throat, the wrench to steady the nerves, the determination to carry on.”
—John Dos Passos (1896–1970)