WHAT IS ENERGY? UNIT 3: ENERGY AND MOTION

I. ENERGY BASICS a.Energy is the ability to do work or cause change b.Work is when a force moves an object c.Force is when an object is pushed or pulled d.Energy is measured in Joules (this is the same unit for work

I. ENERGY BASICS CONT e. Relationship between work and Energy. i. When work is done on an object, some of the energy is transferred to the object. ii. Therefore, the object has gained Energy. f. Example: Your backpack. i. Work: you picking up your backpack ii. Energy Transfer: from your body to the backpack iii. What happens with the Energy transfer: Your backpack moves

I. ENERGY BASICS CONT. g. Power and Energy i. Power is the rate at which energy is transferred, or the amount of energy transferred in a unit of time. ii. Power Equation: Power = Energy Transferred ÷ Time iii. Example: Jerry is building a house, it takes 16 Joules of work to move a cinder block for the walls. It take about 120 seconds to move the cinder block from the pile to the wall location, what is the power of this system?

II. TWO DIFFERENT TYPES OF ENERGY a.First Type: Kinetic Energy i. Kinetic Energy: The Energy an object has due to its motion ii. Factors of Kinetic Energy: 1. Speed: The faster an object is moving, the greater the Kinetic Energy. 2. Mass: As mass increase, Kinetic Energy increases iii. Kinetic Energy Equation:

II. TWO DIFFERENT TYPES OF ENERGY iv. Variables 1. K.E.= Kinetic Energy (Joule) 2. V = speed (m/s) 3. m = mass (kg) always convert into kg v. Kinetic Energy Example: If a car is moving at a speed of 20 m/s and has a mass of 1239 kg, what is the Kinetic Energy of this car? Step 1: Write what you know Step 2: Write what component you are looking for Step 3: Do the math

II. TWO DIFFERENT TYPES OF ENERGY b. Second Type: Potential Energy i. Potential Energy: the energy that an object possess at the state of rest ii. This is the result of the objects position or shape. iii. Potential energy related to an objects height is called Gravitational Potential Energy 1. Equation: Gravitational Potential Energy = Weight x Height a. G.P.E=Wh

II. TWO DIFFERENT TYPES OF ENERGY iv. Example If a book is held 1.5 meters off the ground and has a weight of 7 Newtons, what is the Gravitational Potential Energy of the book?

II. TWO DIFFERENT TYPES OF ENERGY v. Potential Energy related to an objects shape is called Elastic Potential energy 1. This deals with objects that can be compressed or stretched

III. CONSERVATION OF ENERGY a. First Law of Thermodynamics: Energy cannot be created or destroyed b. Second Law of Thermodynamics: Heat can only go from a hotter to a cooler c. Energy only changes form d. Mechanical Energy: the total Kinetic and potential energy in an object i. How to find Mechanical Energy 1. Potential E + Kinetic E

III. CONSERVATION OF ENERGY e. Energy Transformation: change from one form of Energy to another i. Falling Object: the height of the falling object decreases, it loses potential energy and the kinetic energy increases ii. Pendulum: at the highest point there is no movement and therefore only has potential energy. It is at its greatest speed at the bottom of the swing. (greatest kinetic energy)

III. CONSERVATION OF ENERGY f. Thermal Energy: object energy is transferred into thermal energy when the object experiences friction i. This is a total of the kinetic and potential energy of the objects particles ii. The faster the particles are moving the greater the kinetic energy iii. The more heat added to an object the faster the particles move

IV. DESCRIBING MOTION a.An object is in motion when its position changes relative to another object. b.Newton’s First Law of Motion: an object at rest will stay at rest unless acted on by an outside force an object in motion will stay in motion unless acted on by an outside force. c.To decide if an object is moving you must choose a reference point d.Relative Motion: you may be moving at different speeds depending what you are comparing your movement to. i. Example: A tree a tree is stationary relative to the earth, however, it is moving relative to the sun

WARM UP #3 1.What is the First Law of Thermodynamics? 2.What is the second Law of Thermodynamics? 3.How do you find Mechanical Energy? 4. When I add thermal energy to an object what happens to the Kinetic Energy?

V. SPEED AND VELOCITY a. Speed: the distance the object moves per unit of time i. How to find speed: divide distance the object traveled by the time it took ii. Speed= distance/time iii. Example: if a plane travels 548 meters in 2.65 seconds, what is the speed of the plane?

V. SPEED AND VELOCITY b. Average Speed: This is the overall speed and time it takes an object to move a certain distance (Most objects do not move at a constant rate.) i. How to find Average Speed: total distance divided by total time ii. Formula: Average Speed=Total Distance/Total Time iii. Example: A biker went a total distance of 65 km. It took the biker 4.25 hours to complete the bike ride. What was the bikers average speed?

V. SPEED AND VELOCITY c. Instantaneous Speed: Speed at which an object is moving at a given instant in time d. Velocity: Speed and direction of an object i. A storm is moving 25 km/h eastward e. Graphing Motion to find Speed i. Slope: Rise / Run ii. Example: It takes Kara 1.5 minutes to run 200 meters. She is running a 1,400 meter race. Plot and graph the race and find her speed at 600 meters

VI. ACCELERATION a. Acceleration is the rate at which velocity changes i. This changes with increase speed (positive acceleration); decreasing speed (negative acceleration); or changing directions. ii. Formula to Find Acceleration iii. Example: A toy car goes from the stopped position to 9 m/s in 4 seconds, what is the acceleration of the toy car? b. Graphing Acceleration i. Time should always be on the x-axis ii. This is a line graph