# Laboratory Report 4

Experiment 4: Work, Power, and Energy

Laboratory Report

Gerome Simeon, Michael Tiu, Mary Grace Anne Trinidad, Darrel Aaron Udasco Department of Math and Physics

College of Science, UST

España, Manila, Philippines

Abstract

The Experiment entitled “Work, Power and Energy” is about relationship between work and power and the concept of energy. Activity 1 is about power and its relationship with work, the computed power outputs of each member of the group for going up are 118W, 205W, 178W, 222W; for going down, the computed power outputs are -150W, -232W, -195W, -303W.

I. Introduction

Energy is one of the most important concepts in the world of science. In everyday use energy is associated with the fuel needed for transportation and heating, with electricity for lights and appliances, and with the foods we consume (Serway & Vuille, 2012). In this experiment the focus is mainly on mechanical energy, which is the sum of kinetic energy, the energy associated with motion, and potential energy, the energy associated with relative position. The sum of the kinetic energy and the gravitational potential energy remains constant at all times and hence is a conserved quantity (Serway & Vuille, 2012).

In physics, work is done only if an object is moved through some displacement while a force is applied to it. If either the force or displacement is doubled, the work is doubled. Double them both, and the work is quadrupled. Doing work involves applying a force to an object while moving it a given distance.[1] In the experiment, work is demonstrated by a person going up and down a staircase. Work is positive when the applied force is in the same direction as the displacement, otherwise it is negative. Power, the rate at which energy is transferred, is important in the design and use of practical devices, such as electrical appliances and engines of all kinds. The concept of power, however, is essential whenever a transfer of any kind of energy takes place. Power is defined as the rate of energy transfer with time (Serway & Vuille, 2012).

II. Theory

The primary concepts given importance in this experiment are work, power, and energy. Work is defined by the equations:

W=Fx∆X

Where Fx is the x-component of the force F and ∆X=Xf-Xi, is the object’s displacement and W=Fcosθd

where d is the magnitude of the displacement and θ is the angle between the vectors F and the displacement ∆x (Serway & Vuille, 2012). It has an SI unit of joule (J). Power is the rate of energy transfer with time and is defined by the equation: P=W∆t

Where W is the work done and ∆t=tf-ti, is the time interval. In obtaining the work done by person in both going up and going down the stairs, the researchers used the formula (the formula for work done by gravity is also shown): Wupg= Fgrcosθup=-mgh=-Wupperson

Wdowng= Fgrcosθdown=-mgh=-Wdownperson

Energy is defined as the ability to do work. There are variety of forms of energy such as mechanical, chemical, electromagnetic, and nuclear energy. Mechanical energy is the sum of kinetic energy and potential energy. Kinetic energy is the energy associated with motion and is defined as KE=12mv2, where m is the mass and v is the speed of the object squared, while potential energy is the energy associated with relative position. It is defined as PE=mgy; where m is the mass, g= 9.80 m/s2 and y is the height. Energy can then be calculated through the use of the Work- Energy Theorem which states that E=Ekin+Epot

Energy also has a standard unit of joules (J).

In computing for the power of each group member, the researchers used the following equation for power: Pup=Wuppersontup Pdown=Wdownpersontdown

III. Methodology

In this experiment, the researchers used the following materials: * Ruler

* Timer

* Vernier motion sensor

* Logger Pro software

For the first activity, the researchers studied power by first, determining the weight of each...

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