1. Physics Ch 10 & 11

2. EnergyEnergy –is the ability to cause change Two types of energyTwo types of energy –Potential Energy –Kinetic Energy

3. Kinetic energyKinetic energy –Energy in the form of motion –The amount of kinetic energy an object has depends on its mass and its velocity K.E. = ½ (mass)*(velocity) 2K.E. = ½ (mass)*(velocity) 2 JouleJoule –The SI unit used to measure energy –Equivalent to Newton-meter

4. Work Energy in motionEnergy in motion Transfer of energy over a given distanceTransfer of energy over a given distance Force through a distanceForce through a distance

5. Work Work = Force*distance Work is measured in Joules Joule is a Newton-meter J = N * m

6. Work at an angle If you are pushing a lawn mower across the yard, work is only in the x direction. So W = F x *d or W = F cos  d F app  F x = F cos 

7. Work at an angle If you are pushing a box UP an incline plane, work is only in the y direction. So W = F y *d or W = F sin  d F app  F y = F sin 

8. Power The amount of work done in a certain amount of time.The amount of work done in a certain amount of time. The rate at which work is done.The rate at which work is done.

9. Power Power =work =Energy time time time time Power = Force*distance time time

10. Machines Make work easierMake work easier Simple machineSimple machine –Does work in only one direction Complex machineComplex machine –Does work in more than one direction –Combination of more than one simple machine

11. Simple Machines Incline PlaneIncline Plane WedgeWedge ScrewScrew Lever Pulley Wheel & Axle

12. Incline PlaneIncline Plane –Sloping surface that reduces the amount of force required to do work WedgeWedge –An incline plane with sloping sides –A moveable incline plane ScrewScrew –An incline plane wrapped in a spiral around a cylindrical post

13. LeverLever –Bar that is free to pivot or turn about a fixed point PulleysPulleys –Grooved wheel with a rope running along the groove. Wheel & AxleWheel & Axle –2 wheels of different sizes that rotate together

14. A machine where work input equals to work outputA machine where work input equals to work output –Will never exist because of friction W input = W output Ideal Machines

15. Mechanical AdvantageMechanical Advantage –Number of times a machine multiplies the effort force EfficiencyEfficiency –Measure of how much the work input is changed into useful work output Efficiently = W out x 100% W in W in

16. Potential energyPotential energy –Energy stored –Energy of position Elastic potential energyElastic potential energy –Energy stored by things that stretch or compress Chemical potential energyChemical potential energy –Energy stored in chemical bonds between atoms

17. Gravitational potential energyGravitational potential energy –Stored energy (by things above earth) –The amount of GPE an object has depends on its mass, the acceleration due to gravity, and its height above ground. –mass * acceleration due to gravity * height off ground PE = m * g * hPE = m * g * h –Measured in Joules (Newton- meter) *Remember g = 9.8 m/s 2*Remember g = 9.8 m/s 2

18. Reference Levels

19. Energy conversionsEnergy conversions –energy changing from one form to another –Fuels store energy in the form of chemical potential energy. Mechanical energyMechanical energy –the total amount of potential and kinetic energy in a system

20. Law of Conservation of EnergyLaw of Conservation of Energy –Energy may change from one form to another, but the total amount of energy never changes –Energy can neither be created nor destroyed, it just changes forms

21. Law of Conservation of Energy ExampleExample –As a swing moves back and forth, its energy continually converts from kinetic to potential & back –If the energy of the swing decreases, then the energy of some other object must increase by an equal amount –Friction converts some of the mechanical energy into thermal energy.

22. Collisions Elastic CollisionElastic Collision –All of the energy is rebounded after a collision. Inelastic CollisionInelastic Collision –None of the energy is rebounded after a collision.

23. Partially Elastic CollisionPartially Elastic Collision –Some (51 - 99%) of the energy is rebounded after a collision. Partially Inelastic CollisionPartially Inelastic Collision –Some (1 - 49%) of the energy is rebounded after a collision. 0% 50% 100% Elasticity

24. Converting mass into energyConverting mass into energy –You must think of mass as energy when discussing nuclear reactions –The total amount of mass and energy is conserved Nuclear fusionNuclear fusion –Two nuclei are fused together –Takes place in the sun Nuclear fissionNuclear fission –Two nuclei are broken apart.

25. Conservation of energy in your bodyConservation of energy in your body –chemical potential energy from food that is stored in your body is used to fuel the processes that keep you alive CalorieCalorie –used to measure how much energy you get from various foods –One calorie is equivalent to about 4,180 Joules