Presentation on theme: "ENERGY The measure of the ability to do work Conservation of energy -energy can change forms but can not be destroyed -the total amount of energy in the."— Presentation transcript:
ENERGY The measure of the ability to do work Conservation of energy -energy can change forms but can not be destroyed -the total amount of energy in the Universe remains constant!!!!!!!!!!!!!!!! -matter acts the same way (total amount remains constant) **Energy is measured in Joules (label, unit)
Potential and Kinetic Energy Potential energy of an object -stored, ready to use energy -could be because of chemical composition -could be because of position of the object -to calculate chemical potential energy of an object --measure the amount of chemicals in the object The amount of potential energy an object contains is the amount of work the object could do to another object
-to calculate position energy of an object -measure mass x 9.8m/s 2 x height lifted kilogram x gravity(use 10) x meter balance scale x constant x meter stick Kinetic energy of an object -determined by an object’s motion -kinetic energy is the work an object is doing on another object -to calculate motion energy
½ x mass x velocity x velocity.5 x kg x (speed and direction) 2 meters/seconds Velocity is a vector -vectors explain magnitude and direction of an object’s motion -magnitude --how fast -direction --which way -used to predict where the object will be in the future (graph)
The potential energy of an object is equal to the kinetic energy or work that it takes to gain that energy Then it will have that much potential energy to use Other examples 1 2 3 4
Work and Energy The label for energy and work is Joule Joule = Newton x meter force x distance -to find distance --measure with a meter stick -to find force --use a spring scale -force is an amount of weight -gravity pulling on mass creates weight (force) The word work is interchangeable for the words potential and kinetic energy
Mass x gravity = force Kilogram x 9.8m/s 2 = Newton For work to be done, the object must move in the direction of the applied force
Problems to do Kinetic energy problems -1/2MV 2, Joules 1)M = 2kg, V = 10m/s, V = North KE or work being done = ? Joules 2)Meters = 2, seconds = 1, Mass = 4kg. down KE or work being done is = ? Joules
Potential energy problems --mgh, Joules 3) mass = 10kg., height = 5 meters PE or Work it can do is = ? Joules Energy/ Work Problem F X D, Joules (Newton Meters) 4) Force = 30 Newtons, Distance = 5 meters Work or Energy = ? Joules 5) Mass = 10kg., distance = 10meters Work or Energy = ? Joules
Power Rate of work done To calculate -work/time (work divided by time) Work / time Joule seconds Newton X meter force distance Kilogram X 9.8m/s 2 mass X acceleration rate due to gravity
Power is measured in Watts -label Kilowatt hour -how much energy is used in an hour -how electric bill is calculated
Power Problem –Work/time, Watts 6) Workdone = 150Joules, time =50seconds Power = ? 7) Force = 20Newtons, distance =.5meters, time = 1 hour (seconds) Power = ?
Answers 1)(.5) x (2) x (100) = 100Joules, North 2)(4kg) x (2/1 = 2 2 = 4) x (.5) = 8Joules, down 3)(10) x (9.8) x (5) = 490Joules 4)(30) x (5) x = 150Joules 5)(10kg.) x (9.8) x (10) = 980Joules Force 6)150/50 = 3Watts 7)(20Newtons)x(.5meters)/3600sec.=.0028Watts 60sec. In a min.X 60min. In an hour = 3600sec.