Kinetic energy is an energy of a mechanical system which depends on speeds of the movement of each of its points. In other words, kinetic energy represents a difference between the total energy and energy of rest of the considered system, that part of total energy of a system which is caused by the movement. Kinetic energy is divided into energy of forward and rotary motion. Unit of measure of kinetic energy in the SI system is the Joule.
Instruction
1. In case of progress all points of a system (body) have identical speeds of the movement which are equal to the speed of the movement of the center of body weights. At the same time kinetic energy of a system Tpost is equal: Tpost =? (mk Vc2)/2 where mk is body weight, Vc is the speed of the center of masses. Thus, at progress of a body the kinetic energy is equal to the work of body weight on a square of speed of the center of masses, divided into two. At the same time the value of kinetic energy does not depend on the direction of the movement.
2. At rotary motion, when a rotation body? - angular speed of a body. If to substitute the equation determining point speed in expression and to take out the general multipliers for a bracket, we will receive the equation of kinetic energy of a system at rotary motion: Tvr =? (mk? 2 hk2)/2 =? (mk hk2)? 2/2vyrazheniye, taken out in brackets, represents the moment of inertia of a body, concerning an axis around which there is a rotation of a body. From here we will receive: Tvr = (Iz? 2)/2 where Iz is the moment of inertia of a body. Thus, at rotary motion of a body, its kinetic energy is equal to the work of the moment of inertia of a body concerning a rotation axis on a square of its angular speed, divided in half. At the same time the direction of rotation of a body does not affect values of its kinetic energy.
3. In case of a rigid body the total kinetic energy is equal to the sum of kinetic energy of forward and rotary movements: T = (mk Vc2)/2 + (Iz? 2)/2