What type of energy do all things that are in motion have?
kinetic energy
When work is done that does not result in motion, but rather buts something in a position or condition to move, what type of energy has increased?
potential energy
The amount of thermal energy contained in an object depends on what two variables?
Thermal energy is a form of molecular kinetic energy that depends on:
1) the speed of the moving particles (measured as temperature) AND
2) the mass and number of moving particles. (measured as the mass of the substance)
What is the kinetic energy of a 30-kg dirt bike moving at a speed of 10 m/s?
1500 J
What is the gravitational potential energy of a 0.5-kg book resting on the top of a 2-meter-high bookshelf?
10 J
What form of energy is stored in gasoline?
chemical potential energy
A wound-up rubber band and a stretched spring have this form of energy.
elastic potential energy
An object's temperature is proportional to the amount of this energy form.
thermal energy
Light is an example of what form of energy?
radiant (kinetic)
How may mass be considered as a form of energy?
Mass is converted into energy during some nuclear reactions (fusion and fission) following the equation E=mc2.
What do all "non-renewable" energy resources have in common?
They are being used faster than they are created in nature, meaning their supply is decreasing and we will eventually run out of them.
What do all "renewable" energy resources have in common?
They are produced as quickly as we consume them, meaning their supply is constant and we should not run out of them.
Give at least two examples of energy resources that are classified as "non-renewable".
any fossil fuel (coal, oil, natural gas)
nuclear fuels, such as Uranium
Give at least two examples of energy resources classified as "renewable".
wind, hydroelectric, solar, geothermal, biomass
Describe a major advantage and a major disadvantage to using fossil fuels as an energy resource.
Advantages: most are abundant, cheap, and can be used used in any type of climate or location.
Disadvantages: their use generates pollution, they are non-renewable
When you go for a walk, what type of energy do you convert into mechanical energy?
chemical potential energy (calories in the food you eat).
What is "mechanical energy" and under what conditions is it conserved?
Mechanical energy = the kinetic + potential energies of ordinary objects (not including molecules).
ME = KE + GPE + EPE
Conserved in the absence of friction or air resistance.
Describe the energy conversion that takes place as an arrow is shot from a bow.
elastic potential energy ==> mechanical kinetic energy
What energy conversion occurs in the operation of an electric generator?
kinetic ==> electrical
How much kinetic energy will a 1-kilogram pendulum have at the bottom of its swing if it is released from a height of 0.5 meters above its rest position?
KE = GPE = mgh = (1)(10)(0.5) = 5 J
What does the word "conserved" mean as it is used in the law of energy conservation?
Energy cannot be created or destroyed, it may only change forms or transfer between objects.
As two opposite charges or magnetic poles are brought closer together, in what way does the amount of potential energy stored in the electric or magnetic field change?
It decreases since they want to be together.
In Einstein's mass-equivalency equation E=mc2, what does "c" represent?
The speed of light
Describe the energy conversions that take place as a ball bounces several times from the floor after being dropped from rest.
Gravitational energy ==> kinetic energy ==> elastic energy + thermal energy ==> kinetic energy (minus thermal) ==> gravitational energy (minus thermal).
This progression occurs for each bounce. The thermal energy generated with each collision with the floor results in a loss of mechanical energy, resulting in a smaller rebound height with each bounce.
How does the potential energy stored in an electric or magnetic field relate to the distance between two like charges or poles?
The closer together the charges or poles, the greater the potential energy stored in the field.