Notes 5-1 Work, Power, Energy

 Objective: Define work.  Objective: Explain how work and energy are related.  Objective: Calculate work and power. CLE 3202.4.3 Demonstrate the relationships among work, power, and machines.

A. Work Makes Something Move 1. Force is a ______or ______. 2. For work to be done, a force must make something ______. 3. ______is the transfer of ______that occurs when a force makes an object move. B. Doing work 1. For work to occur an object must ______. 2. The motion of the object must be in the ______as the applied force.  When you lift a stack of books, your arms apply a force upward and the books move upward. Because the force and distance are in the same direction, your arms have done work on the books.

C. Force and Direction of Motion  When you carry books while walking, you might think that your arms are doing work. However, the force exerted by your arms does NO work on the books. The force exerted by your arms on the books is upward, but the books are moving horizontally. D. Work and Energy 1. When work is done, a transfer of ______always occurs. 2. This is easy to understand when you think about how you feel after carrying a heavy box up a flight of stairs. 3. Energy is the ability to do ______. 4. Energy is ______from the object that is always ______to the object on which the work is done.

E. Calculating Work 1. The amount of work done depends on: a. the amount of ______b. the ______over which the force is ______. 2. When a force is exerted and an object ______in the direction of the ______, the amount of work done can be calculated as follows: Work = force (in newtons) x distance ______

W = F = D =

3. Work, like energy, is measured in ______. 4. Joule - amount of work done when a force of one Newton acts through a distance of one meter)

F. Calculating Power 1. Power is the amount of work done in ______. 2. It is a ______at which ______3. To calculate power, divide the work done by the time that is required to do the work.

4. The SI unit for power is the ______. One watt equals one joule of work done in one second. W P  t 5. ______= 1 kilowatt (kW) 6. Because the watt is a small unit, power often is expressed in kilowatts. P = ______W = ______t=______

 A figure skater lifts his partner, who weighs 450 N, 1.5 m in 3.0 s. How much power is required? Given Work

G. Work 1. Since work and energy are related, power also can be calculated ______2. Just as power is the ______at which work is done, power is also the rate at which ______is ______. H. Power and Energy When energy is transferred, the power involved can be calculated by dividing the energy transferred by the time needed for the transfer to occur. Power Equation for Energy Transfer:

Questions 1.______is the transfer of energy that occurs when a force makes an object move.

2. The amount of work done depends on what two things?

3. Which of the following equations can be used to calculate power?

4. How are work and energy related?