Euler's laws of motion Euler's laws of motion In classical mechanics, Euler's laws of motion are equations of motion which extend Newton's laws of motion for point particle to rigid body motion. They were formulated by Leonhard Euler about 50 years after Isaac Newton formulated his laws. Euler's first law states that the linear momentum of a body, (also denoted ) is equal to the product of the mass of the body and the velocity of its center of mass : Internal forces between the particles that make up a body do not contribute to changing the total momentum of the body as there
Gravity knife Gravity knife A gravity knife is a knife with a blade contained in its handle, and which opens its blade by the force of inertia ("centrifugal" force) or gravity. As the gravity knife requires gravity or spinning motion to propel the blade out of the handle, it differs fundamentally from the switchblade, which opens its spring-propelled blade automatically upon the push of a button, switch, or fulcrum lever. The main purpose of this opening method is that it allows opening and closing to be done "one handed", in situations where the other hand is occupied. A major historical use has