Conservation of Energy Flashcards
What is the equation for gravitational potential energy?
Mass x gravitational field strength x height
What is the equation for kinetic energy?
1/2 x mass x (velocity)^2
What is meant by the conservation of energy?
The total amount of energy in a closed system remains constant and energy cannot be made or destroyed but can change from one form to another
What are the changes in the total energy of a ball that is kicked, assuming that no external forces act?
The total energy of system remains constant due to the conservation of energy
What are the energy changes that occur in a filament light-bulb?
Electrical energy is transferred into light and heat energy then light is useful energy form and heat is waste energy
What are the energy transfers for a bungee jumper?
When falling, the GPE is converted to KE of jumper, as the cord tightens, KE is converted and stored as EPE and at lowest point, the jumper’s initial GPE equals the EPE stored in the cord
Why does a bungee jumper slows down once the cord begins to stretch?
Kinetic energy decreases since it is converted to EPE and since KE is proportional to (velocity)^2, as KE decreases so does velocity
What is waste energy?
The energy that isn’t used by the device for its desired purpose, or not converted into the desired form
What are two equations to calculate efficiency?
Useful output energy (output energy) / total input energy (power output)
What are the consequences for energy transfer of a material with a high thermal conductivity?
The rate of energy transfer through the material is higher than for a material with a lower thermal conductivity
Do double-glazed windows have a higher or lower thermal conductivity than single-glazed windows?
Lower, meaning less energy transfers through them
What are the three methods of reducing heat loss in a building?
Double glazing, loft and wall insulation and thicker walls
How can you reduce unwanted energy transfer in a mechanical system?
Reduce friction by lubricating moving parts
How can the efficiency of a system be increased?
Reducing and recycling waste output
What is a renewable energy resource?
An energy source which can be replenished as its being used up
What are four examples of renewable energy resources?
Hydro-electricity, wind, tidal and solar energy