9.4 Guided ReadingName:
“Conservation of Energy”
1) On a roller coaster all of the required for the entire ride comes from the work done by the as it lifts the cars and the passengers.
2) The energy from the initial work is stored as energy at the top of the hill. After that the energy goes through a series of from kinetic and potential energy.
3) A small amount of this energy is transferred as heat to the and as vibrations produce a roaring in the air.
4) In the roller coaster the potential energy changes to kinetic energy as the car downward. At the bottom of the hill the car has a of kinetic energy and a of potential energy.
5) When the car reaches the lowest point the system has no energy because the car cannot go any .
6) As the car uses the kinetic energy to climb the hill it slows down and most of the energy turns into energy as the of the car increases.
7) The car cannot climb a hill than the first one without an extra boost. There is not enough extra .
8) A player bouncing a tennis ball who throws the ball down adds energy to the ball. This energy as the ball falls and energy changes.
9) As the ball bounces the kinetic energy changes to energy and quickly changes back to kinetic energy as the ball bounces back .
10) The ball’s on return will be the same at which it was thrown down. If it is dropped instead of thrown it will bounce to the same from which it was dropped.
11) A roller coaster car loses mechanical energy due to and . When energy seems to disappear it has really just changed to a form.
12) Energy will continually forms. The Law of Conservation of Energy says energy cannot be or .
13) When the total energy in a system it must be due to energy that enters the system from an source.
14) When studying energy scientist often limit their view to a area & those boundaries define a .
15) When the flow of energy is small enough to be ignored it is a system. Most systems are and exchange energy with the outside.
16) There is a difference between the work done by a machine and the work done. is a measure of how much useful work it can do.
17) Efficiency is measured in a . A machine with 100 percent efficiency produces as much useful work as the work done on the .
18) A machine designed to keep going forever without any input energy is a . If they did exist they would require the absence of .
Efficiency Examples * Multiply by 100 to get a %
A certain light bulb consumes 200J of electrical energy per second, but only emits 25J of light energy per second. Calculate the efficiency of this bulb.
A certain large wind turbine is able to transform 1,500,000J of mechanical energy into 1,000,000J of electrical energy every second.
- How much thermal energy does this turbine 'waste' each second?
- Calculate the efficiency of this turbine.
A certain motor uses 1300J of energy to raise a 30kg mass to a height 2.4 meters above where it started.
- How much potential energy does the mass gain during the lift?
- Calculate the efficiency of this motor.