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Learning Objectives. 7.1. Work: The Scientific Definition. Explain how an object must be displaced for a force on it to do work. Explain how relative directions of force and displacement determine whether the work done is positive, negative, or zero. 7.2. Kinetic Energy and the Work-Energy Theorem.
This equation is called the work–kinetic energy theorem. Thus, continuing with the example of falling body, the work performed on the body results in an increase of its kinetic energy.
Work W is the energy transferred to or from an object by means of a force acting on the object. Energy transferred to the object is positive work, and energy transferred from the object is negative work.
W Work J EK Kinetic energy J EP Potential energy J EM Mechanical energy J F Force N x Displacement m r Distance m h Hight m M, m Mass kg Force-displacement angle ° v Speed m/s vm Mean speed m/s g Gravitational acceleration 2 (9.8 m/s in Earth surface) m/s2 G Gravitational constant: 6.67·10 11 N·m 2/kg k Elastic constant of the spring N/m p ...
Energy is defined as the capacity to do work and comes in different forms: Gravitational potential energy - this is dependent on the object’s position in a gravitational field and its mass.
Work W and Energy E. A body that has energy may transfer some, or all, of its energy to another body. The total amount of energy remains constant (conserved) even if it has been transformed to another type. The amount of energy transformed (∆E) is called work W. The body losing energy does work, the body gaining energy has work done on it.
Work-energy theorem: The net/total work done on an object is equal to the change in the object’s kinetic energy. In symbols: Wnet = ∆ EK. 2 Wnet = 2m(vf. - vi 2) Conservative force: The work done by the force in moving an object between 2 points is independent of the path taken ex. gravitational, electrostatic and elastic forces.
