Work and Power
- 1. Bellwork: What do you think are the differences between work and power?
- 2. Title of Cornell Notes Work and Power
- 3. What is work? Work- A force acting through a distance. The distance that the object moves must be in the same direction as the force applied to the object. Lifting Force Movement Distance What force is having to be overcome by the lifting force? Gravity- Weight! Weight
- 4. Work Work- A force acting through a distance. The distance that the object moves must be in the same direction as the force applied to the object. Pushing Force Distance Moved What force is having to be overcome by the pushing force? Friction!
- 5. Lifting Force Movement Distance Work is not done every time a force is applied. Work is done only when a force moves an object in the same direction as the applied force. Is the man doing work when he lifts the box? Yes. Is the man doing work when he holds the box? No! Is the man doing work if he carries the box? No! (But he IS applying a force) (But he IS applying a force)
- 6. Work Think about pushing on wall that does not move. A force is applied but the wall has not moved a distance. Is work done? Only when an object moves No! But I did expend energy applying a force!
- 7. Calculating Work Work = force (N) x distance (m)or Displacement W = F x D The unit for work is a Joule (J). If you lifted an object weighing 1N through a distance of 1m, you did 1 Joule of work: W = FD = 1N x 1m = 1 J A Newton is about ¼ of a pound. Is a Joule of work…very much work? No!
- 8. Calculating Work If you lifted an object weighing 200 N through a distance of 0.5m, how much work would you do? Work = force x distance = 200 N x 0.5m = 100 J.
- 9. What is power? Power is the rate at which work is done, or the amount of work per unit of time. Two men can move a lot of sand using shovels…
- 10. Power Power is the rate at which work is done, or the amount of work per unit of time. Two men can move a lot of sand using shovels… …but a front-end loader can do it in less time… …because the front-end loader has more POWER.
- 11. Power Power is the rate at which work is done , or the amount of work per unit of time. Power = work / time or Power = force x distance / time Because work = force x distance
- 12. Power The unit for power is watt (W). One watt is equal to 1 joule per second (1 J/sec). Large quantities of power are measured in kilowatts (kW). One kilowatt equals _____ watts. One million watts is a megawatt 1000
- 13. Summary Create a Venn Diagram comparing work and power