Work, Energy, and Power: A Reviewer

WORK, ENERGY, AND POWER 4.2 | SCIENCE | QUARTER 04 2023 3. Work may either be negative, zero, or positive. WORK 4. The unit of work is newton x meter (N x m ), also known as ● The product of the joule (J), named in honor of the force British applied to move an object and the displacement in ● The measure of how a force is 1Nxm=1J 5. When centimeter-gram-second capable of moving an object, (CGS) units are used, the unit or in causing a displacement. work is erg. 1 dyne x cm = 1 erg Calculating Work ● To James Prescott Joule. the direction of that force. physicist, calculate work W, we multiply the force F by the displacement d ENERGY W = Fd ● Displacement is a measure of how far (distance) an object move The capacity to do work. ● It takes energy to be able to do work. while considering the direction of motion. Energy of moving bodies is called ANALYZING AND CALCULATING THE WORK DONE BY A FORCE: 1. ● mechanical energy ● Kinetic energy ● Potential Energy You must know the direction of the force. KINETIC ENERGY (KE) 2. You must know the direction of motion relative force. parallel to force? Is it the Is it perpendicular to the force? Is it an angle with respect to the force? — energy of motion ● To calculate the kinetic energy K or KE of an object, we use mass m and speed v in the formula Reviewer by: Khasandra Chloe S. Serrano 1 WORK, ENERGY, AND POWER 4.2 | SCIENCE | QUARTER 04 2023 In equation form… POTENTIAL ENERGY — K.E = ½ mv² ● The units of work and energy are the same RELATIONSHIP AND ENERGY ● If the energy of position or Two Types: Gravitational potential energy BETWEEN work the configuration is WORK positive, Elastic potential energy it Gravitational Potential Energy increases the kinetic energy of (GPE) the object ● If the work is negative, it decreases the kinetic energy of the object. ● If the work done is zero, it has no effect on the kinetic energy on the kinetic energy of the object. It neither adds or takes away energy from it. ● To sum up, we say that the total work done on an object is equal to the change (represented by the symbol or delta) in its kinetic energy, or in equation form: This is known the energy stored because of elevation (or vertical height) • It is given by the equation: Ug = mgh Where: • m is the object’s mass • g is the acceleration due to gravity (9.8 m/s2) • h is the height. • SI unit of GPE is joule (J) • For any given mass, gravitational W=∆K ● • potential energy is higher as the work-energy relationship or the work-energy theorem when the position is higher. • An object with potential energy may or may not be moving. Thus, any object which has gravitational potential energy can do work when allowed to fall. Reviewer by: Khasandra Chloe S. Serrano 2 WORK, ENERGY, AND POWER 4.2 | SCIENCE | QUARTER 04 2023 Elastic Potential Energy (EPE or Ue) CONSERVATION OF ENERGY • In physics, an elastic object has to • fulfill an important requirement: be manufactured by source; it has to be able to return to its original shape and converted size. useful form. • Hooke’s law, which states: Conservation of Mechanical Energy Within • the elastic limit, the force Energy is from mechanical applied to stretch or compress a converted spring is directly proportional to the potential not something something energy between into a can kinetic be and change in its length. Law of Conservation of Energy (LCE) • In equation form, Hooke’s law looks like this: • perfect handover from one form of F = kx energy to another • “Conservation” - involves a quantity Where: F is the applied force; that remains the same even as X is the change in length; and k is the other quantities change force constant “Energy can neither be created nor • When you stretch a spring, you are destroyed. It can only be converted doing work on it and storing from one form to another.” potential energy. The elastic potential energy is given the POWER equation: U = ½ k∆x² U = elastic potential energy k = spring constant ∆x = change in position • The unit of EPE is joules or erg. • From the definition of power, we can write the equation as: P=W t where W is the work done in joules and Reviewer by: Khasandra Chloe S. Serrano 3 WORK, ENERGY, AND POWER 4.2 | SCIENCE | QUARTER 04 2023 t is the time it takes in seconds. The the resulting unit is the joule per second (J/s) or watt (W). • Recall that work is given as W = Fd. If we substitute this to the expression of power, we get: P = Fd T =Fxd t • Knowing that d/t is the average speed (or actual speed if it is uniform), then we can also calculate power using the equation: P = Fv where v stands for the average speed. • A powerful machine can pull or push harder and can move things faster. • The human body can be considered a machine, converting energy and doing work. • Electrical appliances have power ratings, too. This is related to how fast the device can convert energy. Reviewer by: Khasandra Chloe S. Serrano 4