Ch. 4 Energy

1
Ch. 4 Energy

• How is work defined?
• Work is done when a force causes an object to be
  displaced.
• Work is expressed in Joules.
• A joule is the work done when one Newton of force
  acts through a distance of 1 meter.
• 1 J 1 N-m

2

• Kinetic energy is moving energy.
• What 2 factors determine the amount of kinetic
  energy an object has?
• 1. Mass of a moving object.
• 2. Speed of the object.
• Potential energy is what kind of energy?
• Stored energy

3

• How does potential energy change to kinetic
  energy?
• Ex. Swinging Pendulum
• Mechanical Energy is the total amount of kinetic
  and potential energy in a system.
• Mechanical Energy P.E. K.E.
• Formula for Work ? W f x d
• Work occurs when an object moves.

4

• Law of conservation of energy states that energy
  can neither be created nor destroyed, but can
  only be converted from one form to another.
• Why is this true?
• In order to make energy you must put energy into
  it.
• Doesnt apply to nuclear energy.

5
Sources of Energy

• How was energy produced to run textile mills so
  that flour, fabrics, and other products could be
  produced before electricity was invented?
• The flow of running water
• We use the same concept today in the dams we
  build. We use more energy efficient dams to
  produce more electricity.

6

• The water flows up to a power station, then falls
  to the bottom of the dam and causes the
  turbine(s) to turn, which creates electricity.
• As the turbine turns a huge generator is
  connected to the shaft of the turbine and it
  stores the kinetic energy as electricity.

7

• Energy that is obtained from falling water is
  called hydroelectric energy.
• Niagra Falls is an example of source of
  hydroelectric energy. This lowers the cost of
  electricity in that area.
• Does anyone know which dam produces the most
  electricity in the U.S.?
• Hoover Dam

8

• What is power?
• The rate at which work is done
• What is the difference between power work?
• Power depends on the amount of time it takes
  work doesnt.
• The faster the work is done the more power there
  is.
• Power is measured in watts

9

• 3 things power is dependent on
• 1. Force applied
• 2. The distance in which the force moves
• 3. How long it takes
• What is a watt?
• It is a unit of power in the metric system
• 1 watt 1 J/sec.
• 1 kilowatt 1,000 watts
• 1 horsepower 746 watts

10

• Pg. 115 ? Calories used in 1 hour.