Work, Energy and Power 2024 PDF

WORK, ENERGY AND POWER  OBJECTIVES 1. Determine the work done by a force acting on a system 2. Relate the work done by a constant force to the change in Kinetic energy of a system 3. Calculate sample problems (work, energy and Power) ACTIVITY 1. Does working hard in your studies always...

WORK, ENERGY AND POWER  OBJECTIVES 1. Determine the work done by a force acting on a system 2. Relate the work done by a constant force to the change in Kinetic energy of a system 3. Calculate sample problems (work, energy and Power) ACTIVITY 1. Does working hard in your studies always leads to excellence? 2.How does knowing about power help you be a better leader in your group? What is work?  WORK DEFINITION FORMULA Work is done when a force Work(W) = Force (F) x distance (d) is applied to an object and -use it when referring to work is done -W=F x d the object moves in the direction of the force. -W= F x d x cosθ -use it when there is angle Reference: Halliday, D., Resnick, R., & Walker, J. UNIT (2018). Fundamentals of Physics (10th ed.). Wiley. JOULE (J) Sample Problem A student pushes a shopping cart with a force of 50 N for a distance of 10 meter in the supermarket. How much work is done by the student? Given Solution Force: 50 N W= F x d distance: 10 m = 50 x 10 Formula = 500 J W= F x d The work done by the student is 500 Joules. Sample Problem A student pushes a box with a force of 100 N at an angle of 30 degrees to the horizontal for a distance of 5 meter. How much work is done on the box? Given Solution Force: 100 N W= F x d x cosθ distance: 5 m = 100 x 5 x cos(30°) Angle: 30° Formula = 433 J W= F x d x cosθ The work done on the box is 433 Joules  What is energy? How does the energy from food help you in physical activities at school?  ENERGY TYPES OF ENERGY: 1.Kinetic Energy (KE): Energy of motion. Energy is the ability to do Formula: KE = 1/2 mv², where m is mass work. It exists in various and v is velocity. forms, which can be converted from one form to 2. Potential Energy (PE): Stored energy due to another. an object’s position or condition. UNIT:JOULE (J) Formula: PE = mgh, where m is mass, g is the acceleration due to gravity (9.81 m/s²), and h is height. 3. Mechanical energy- the energy of motion and positon and the sum of two types of  Sample Problem (Kinetic energy) A student rides a bicycle with a mass of 15 kg at a speed of 5 m/s. What is the kinetic energy of the bicycle? Given Solution mass : 15 kg KE= 1 mv² velocity: 5 m/s 2 Formula = 1 ( 15)(5)² KE= 1 mv² 2 2 = 187.5 The kinetic J of the energy bicycle is 187.5 Joules.  Sample Problem (Potential energy) A student climbs a staircase to reach the second floor of their school, which is 5 meter high. If the student has a mass of 60 kg, what is the potential energy gained at the top of the stairs? Given Solution mass : 60 kg PE= mgh gravity: 9.81 m/s² = (60)(9.81)(5) height : 5 m = 2,943 J Formula PE= mgh The potential energy gained  WHAT IS ENERGY CONSERVATION?  Law of Conservation of IMPORTANCE energy: Energy cannot be created Reduces environmental impact or destroyed; it can only be (less pollution and resource depletion). transformed from one form Saves money (lower energy to another. In a closed bills). system,the total amount of Enhances energy security by energy remains constant reducing reliance on over time. non-renewable resources. Why do we need to conserve energy?  Formula To find velocity To find mechanical For conserve Kinetic energy energy v= √2 KE KE= ME- PE m ME= PE+ KE Kinetic energy Potential energy KE = 1/2 mv² PE= mgh  g= 9.81 m/s² Point C Point D Point B PE= mgh PE= mgh Point A PE= mgh = (3)(9.81)(0) = (3)(9.81)(5) PE= mgh = (3)(9.81)(5) =0J =147.15 J = (3)(9.81)(8) =147.15 J KE= ME- PE KE= ME- PE =235.44 J KE= ME- PE = 235.44 J – 147.15 J = 235.44 J – 0 J KE= ½ mv² = 235.44 J – 147.15 J = 88.29 J = 88.29 J = 235.44 J =1/2(3)(0)² ME= PE+ KE ME= PE+ KE ME= PE+ KE =0J = 235.44 J + 0 J = 235.44 J + 0 J = 235.44 J + 0 J ME= PE+ KE = 235.44 J = 235.44 J = 235.44 J = 235.44 J + 0 J v= √2 KE v= √2 KE v= √2 KE = 235.44 J m m m v= 0 m/s =√2(88.29) =√2(88.29) =√2(235.44) 3 3 3 =√58.86 =√58.86 =√156.96 v= 7.67 m/s v= 12.53 m/s v= 7.67 m/s  POWER Power is the rate at which work is done or energy is transferred. It FORMULA AND UNIT tells us how quickly work can be done. Formula: Power (P) = Work (W) / Time (t) Units: Measured in Watts (W)  Sample Problem A student does 600 Joules of work lifting their backpack up a flight of stairs in 3 seconds. What is the power output of the student? Given Solution Work : 600 J P= W/t Time: 3 s = 600/3 = 200 W Formula P= W/t The power output of the