Work, Power, and Energy

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Experiment 4: Work, Power and Energy
Maria Isabela Mendoza, Carmela Miranda, Arianne Nagrampa, and Vivien Oreo Department of Biological Sciences
University of Santo Tomas
España, Manila, Philippines

Abstract
The experiment performed involved work, power and energy. On the first activity, the time it took for each member to go up and down the stairs was recorded. Afterwards, the work and power done were computed. The most powerful member in the group was student number 2 with power outputs of 239.4 W and 266.0 W when going up and down respectively. On the second activity, the graphs of the potential energy vs. time, kinetic energy vs. time, and mechanical energy vs. time of a ball thrown vertically were all predicted. Finally, the ball was tossed on the motion detector and the graphs of potential, kinetic, and mechanical energies vs. time were all produced using the Logger Pro. Introduction

Work is said to be an act of exerting force. Whatever it is that can make us tired is considered work. The similarity between the conventional meaning and the mathematical meaning of Work is movement. Mathematically, work is defined as W = Fd, where F is the magnitude of the force applied and d is the displacement of the object where force was applied on. Work can be positive or negative; this is due to the positive or negative nature of F and d. When work is positive, this implies that the F and d are of the same sign. This means that the mechanical energy is increased by work in the object. Work is negative when either the value of F or d is negative. This implies that the mechanical energy is lost. Mathematically speaking, Power is the rate at which energy is transmitted. In everyday life, we can explain power through the function of the things around us. The mere action of turning the light on demonstrates power. The unit for power or P is joule per second (watt) which directly means W done per second. Energy is everywhere, in our bodies and out in the environment. The Conservation of Energy explains that just like heat, energy can neither be created nor destroyed. Instead, energy is transmitted into different types. All kinds of matter contain a lot of energy that they reuse and recycle into the specific type of energy that will enable them to do work. Two of the most widely discussed types of energy are kinetic (KE) and potential (PE) energy, especially in Physics. These types of energy are essential in understanding motion and the universe in general. This study aims to: (1) demonstrate the Law of the Conservation of energy, (2) measure the change in kinetic and potential energies as a ball moves in free fall and (3) determine power output when going up and down the stairs.

Theory
In calculating for Work done by gravity on a person this formula is followed: W(work in Joules)= (force in Newton) (distance in meter) cosΘ, where Θ is the smaller angle between force and distance.

In calculating for the power output this formula is followed: P(power in watt)= W(work in joules)/ t(time in seconds).
Methodology
In this experiment, the materials used were bathroom scale, set of weight, timer. .Activity 1 (power)
The weight of each group member was determined. Each group member was asked to climb up and down the stairs recording its time. The height of the stairs was measured. Using the following data the Work done by each of the member going up and down the stairs was computed along with the power used. Activity 2 (Energy of a tossed ball)

A graph of potential energy versus time of a ball thrown vertically upwards, a graph of a mechanical energy versus the time of the same ball, and a graph of kinetic energy versus time of the same ball was predicted. Given the predicted data the graphs were compared to the actual graph given by using the motion detector to show the actual energy given by the ball being thrown upwards.

Results and Discussion
In Physics, work is an activity that involves force and its movement...
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