# Work, Energy And Power

## Overview

To delve into this captivating topic, we will begin by exploring the fundamental concepts of work, energy, and power. Work is defined as the transfer of energy resulting from the application of a force over a distance. It is an essential aspect of understanding how energy is utilized in various mechanical systems. Energy, on the other hand, is the capacity to do work. In this course module, we will unravel the intricate relationship between work and energy and how they are interrelated in different physical scenarios. One of the key objectives of this course is to comprehend the intricacies of calculating work done in lifting a body and by falling bodies.

When a body is lifted against the force of gravity, work is expended in overcoming this gravitational pull. Additionally, as objects fall, gravitational potential energy is converted into kinetic energy, resulting in work being done by the falling bodies. Through practical calculations and theoretical derivations, we will master the art of quantifying these energy transformations. Moving forward, we will embark on a journey to derive the formulas for Potential Energy (PE) and Kinetic Energy (KE). Potential Energy is the energy possessed by an object due to its position relative to other objects, while Kinetic Energy is the energy an object possesses due to its motion.

These energy forms play a pivotal role in understanding the conservation of mechanical energy, a principle we will verify and apply rigorously throughout this course. An integral part of our exploration will involve identifying the diverse types of energy that a body can possess under different conditions. From gravitational potential energy to elastic potential energy, we will uncover the myriad forms of energy and how they manifest in various scenarios. Moreover, we will discuss the unit of energy, the Joule (J), and how it relates to electrical consumption, measured in Kilowatt-hours (KWh). Furthermore, we will dissect the concept of power as the time rate of doing work.

Power signifies how quickly work is done or how energy is transferred in a specific timeframe. Understanding the unit of power, the Watt (W), is crucial in grasping the efficiency and performance of different mechanical systems and machines. As we progress, we will delve into the intricate world of machines and mechanical advantage. From levers and pulleys to inclined planes and gears, we will unravel the inner workings of these simple machines and their components.

We will analyze the force ratio (F.R), mechanical advantage (M.A), velocity ratio (V.R), and efficiency of machines, elucidating how these factors impact the overall performance of mechanical systems. Moreover, we will explore the effects of friction on machines and techniques to mitigate frictional losses. Friction poses a significant challenge in mechanical systems, leading to energy losses and decreased efficiency. By understanding the strategies to reduce friction and enhance machine performance, we will elevate our knowledge of energy conservation and optimization in practical applications.

In conclusion, this course on Work, Energy, and Power will equip you with the foundational principles and analytical tools to navigate the dynamic realm of mechanical energy transformations and machine operations. Prepare to delve into the heart of physics, where energy governs the intricacies of motion, work, and power. Let's embark on this enlightening journey together! [[[Include a diagram illustrating the relationship between work, energy, and power in a mechanical system.]]]

## Objectives

1. Calculate work done in lifting a body and by falling bodies
2. Identify and explain the unit of energy and power
3. Derive potential energy (PE) and kinetic energy (KE)
4. Identify different types of energy possessed by a body under given conditions
5. Understand the concept of work, energy, and power
6. Explain the effects of friction on machines and ways to reduce it
7. Recognize simple machines and their components
8. Verify the principle of mechanical energy conservation
9. Analyze the force ratio (FR), mechanical advantage (MA), velocity ratio (VR), and efficiency of machines

## Lesson Note

In the realm of Physics, the concepts of work, energy, and power are fundamental. These concepts are interconnected and play a vital role in understanding the world around us. Let's dive deeper into these concepts, exploring how to calculate work, recognize types of energy, derive important equations, and comprehend the principles of machines.

## Lesson Evaluation

Congratulations on completing the lesson on Work, Energy And Power. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

1. What is the SI unit of energy? A. Watts B. Newton C. Joules D. Ohms Answer: C. Joules
2. Which of the following is a form of mechanical energy? A. Heat energy B. Light energy C. Sound energy D. Kinetic energy Answer: D. Kinetic energy
3. Which of the following correctly defines the concept of power? A. The ability to do work B. Rate of energy transfer C. Force exerted over a distance D. Potential energy due to position Answer: B. Rate of energy transfer
4. What is the unit of electrical consumption? A. Watts B. Joules C. Ohms D. Kilowatt-hour Answer: D. Kilowatt-hour
5. Which machine component is a simple machine used to change the direction of an applied force? A. Lever B. Pulley C. Inclined plane D. Screw Answer: B. Pulley
6. Which type of energy is associated with an object at rest at a certain height above the ground? A. Kinetic energy B. Gravitational potential energy C. Thermal energy D. Electrical energy Answer: B. Gravitational potential energy
7. In a frictionless environment, what can be said about the mechanical energy of a system? A. Mechanical energy is constant B. Mechanical energy decreases C. Mechanical energy increases D. Mechanical energy becomes zero Answer: A. Mechanical energy is constant
8. Which of the following is not a type of simple machine? A. Wheel and axle B. Screw C. Gears D. Wire Answer: D. Wire
9. What is the unit of power? A. Joules B. Watts C. Newton D. Kilowatts Answer: B. Watts
10. Which parameter determines the efficiency of a machine? A. Force ratio (F.R) B. Mechanical advantage (M.A) C. Velocity ratio (V.R) D. Frictional losses Answer: D. Frictional losses

## Past Questions

Wondering what past questions for this topic looks like? Here are a number of questions about Work, Energy And Power from previous years

Question 1

You are provided with a battery of e.m.f, Estandard resistor, R, of resistance 2 Ω $\mathrm{\Omega }$, a key, K, an ammeter, A, a jockey, J, a potentiometer, UV, and some connecting wires.

(i) Measure and record the emfE, of the battery.

(ii) Set up the circuit as shown in the diagram above with the key open.

(iii) Place the jockey at the point, U, of the potentiometer wire. Close the key and record the reading, i, of the ammeter.

(iv) Place the jockey at a point on the potentiometer wire UV such that d = UT = 30.0 cm.

(v) Close the circuit, read and record the current, I, on the ammeter,

(vi) Evaluate I1 ${}^{1}$.

(vi) Repeat the experiment for four other values of d = 40.0 cm, 50.0 cm, 60.0 cm and 70.0 cm. In each case, record I and evaluate I1 ${}^{1}$.

(vii) Tabulate the results

(ix) Plot a graph with d on the vertical axis and I on the horizontal axis stalling both axes from the origin (0,0).

(x) Determine the slope, s, of the graph.

(xi) From the graph determine the value I1 ${}_{1}$, of when = 0. (ci) Given that=s, calculate 8.

(xii) State two precautions taken to ensure accurate results.

(xii) Given that Eδ $\frac{�}{�}$ = s, calculate δ $�$.

(b)(i) Write down the equation that connects the resistance, R, of a wire and the factors on which it depends. State the meaning of each of the symbols.

(ii) An electric fan draws a current of0.75 A in a 240 V circuit. Calculate the cost of using, the fan for 10 hours if the utility rate is \$ 0.50 per kWh.

Question 1

A piano wire 50 cm long has a total mass of 10 g and its stretched with a tension of 800 N. Find the frequency of the wire when it sounds its third overtone note.

Question 1

A ball of mass 0.1kg moving with velocity of 20ms-1 is hit by a force which acts on it for 0.02s. If the ball moves off in the opposite direction with a velocity of 25ms-1 , calculate the magnitude of the force.

Practice a number of Work, Energy And Power past questions