Topic 8 - Energy: Forces doing work Flashcards
State the law of energy conservation
Energy cannot be created or destroyed, only transferred into different forms.
State any changes in the total energy of a ball that is kicked, assuming that no external forces act
The total energy of the system remains constant due to the conservation of energy
Describe the energy changes that occur in a filament light-build.
Electrical energy is transferred into light and heat energy
Describe the energy transfers for a bungee jumper
When falling, GPE is converted to KE of jumper
As core tightened, KE is converted and stored as elastic potential energy
At lowest point, jumpers initial GPE equals the EPE in the cord.
Explain why a bungee jumper slows down once the cord begins to stretch
Kinetic energy decreases since it is converted to elastic potential energy
Since KE is proportional to velocity squared, as KE decreases, so does velocity
Describe the energy changes in a power station
Heat energy released in the reaction heats water to make steam. Steam moves the turbine, converting kinetic energy
Kinetic energy turns the generator
Electrical energy generated
In what ways can the energy of a system be changes?
Through heating
Through electrical input
Through work done by forces
How can energy be changed through work done by forces?
A force which moves an object (kinetic energy) causes work to be done over a distance
What equation is used to measure the work done on an object?
Work done = force x distance
Why do wasteful mechanical processes cause a rise in the temperature of the surroundings?
They cause energy to be transferred by heating the surroundings
What is the equation for kinetic energy?
Energy = 1/2 x mass x velocity squared
What is the equation for gravitational potential energy?
Energy = mass x height x gravitational field strength
What is the definition of power?
The rate at which energy is transferred
State two equations for power
Power = energy transferred /time Power = work done/time
What is the unit of power?
Watt
