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Experiment 4: Work, Energy, and Power
Laboratory Report

Group 5

Department of Mathematics and Physics
College of Science, University of Santo Tomas
España, Manila, Philippines

Abstract
The concept of energy is central to physics, as many times the analysis of a system's motion involves understanding how energy is changing. The change in energy is known as work, and the work done over a given period of time is known as power. This concept was applied in this experiment.

Introduction
Work can be defined as transfer of energy. In physics we say that work is done on an object when you transfer energy to that object. If one object transfers energy to a second object, then the first object does work on the second object. Work is the application of a force over a distance. Force, on the other hand, is equal to the weight of the object, and the distance is equal to the height of an object. Energy can be defined as the capacity for doing work. The simplest case of mechanical work is when an object is standing still and we force it to move. The energy of a moving object is called kinetic energy. Power is the work done in a unit of time. In other words, power is a measure of how quickly work can be done. The unit of power is the Watt = 1 Joule/ 1 second. One common unit of energy is the kilowatt-hour (kWh).

After knowing the definitions of the terms and the equations to be applied, we now proceed to our main objectives in this experiment, which are: (1) To demonstrate conservation of mechanical energy; (2) To measure change in kinetic and potential energy as a ball moves in free fall; (3) And to determine power output when going up and downstairs.

Theory

Energy - It is one of the most important concepts in the world of science. It is the capacity of a physical system to do work (Jones). This experiment involves mechanical energy. Mechanical energy is the sum of kinetic energy (energy at motion) and potential energy (energy at rest). Work - It is done only if an object is moved through some displacement while a force is applied to it. Work is equal to force times displacement. W=Fd

Where, F = magnitude of the force acting on the object; d = magnitude of the object’s displacement. This formula is used when the force is constant and parallel to the displacement, which must be along a line. The formula W= FxΔx where Fx is the x-component if the force and Δx is the object’s displacement may also be used. The SI unit of work is Joule (J). It is equal to (kg x m2)/s2.

Work done on an object that involves an inclined plane may be computed using the formula W=FcosΘd
Where, W = work; F = magnitude of force; Θ = angle between vectors; d = magnitude of the displacement Wup= -mgh
or
Wdown= mgh

Another formula for work where m = mass; g = gravity; h = height
Conservation of Mechanical Energy - When a physical quantity is conserved, the numeric value of the quantity remains the same throughout the physical process. Although the form of the quantity may change in some way, its final value is the same as its initial value (Serway & Vuille, 2011). KEi+ PEi= KEf+ PEf

According to the equation above, the sum of the kinetic energy and the gravitational potential energy remains constant at all times and hence is a conserved quantity (Serway & Vuille, 2011).
In any isolated system of objects interacting only through conservative forces, the total mechanical energy of the system remains the same at all times (Serway & Vuille, 2011).
Kinetic Energy is the energy that an object possesses because of its motion (http://hyperphysics.phy-astr.gsu.edu/hbase/ke.html). The kinetic energy of an object of mass m is moving with a speed v is KE= 12mv2

Work-energy theorem:
Wnet= ΔKE
where the change in kinetic energy is due entirely to the object’s change in speed.
Potential Energy is the energy while the object is at rest. The gravitational potential energy of a system consisting of Earth and an object of...
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