Work, Power and Effiency Flashcards
How is work done?
Work done is when a force is applied and an object is moved a distance - this transfers energy
What is the calculation for work done?
Work done(J) = force(N) x distance(M)
what would we deffine a joul?
1 joule is the energy transfered when a force of 1N causes a displacment of 1m
What properties does a moving object have?
mass and velocity
How do we calculate the amount of energy in the kinetic store of an object?
Kinetic energy = 1/2 x mass x velocity(squared)
What is the elastic potenial energy store of an object?
The elastic potential store of an object relates to how stretched it is. The more stretched it is, the more energy it has in the elastic store
How would we calculate the amount of energy in the elastic potentail store of an object?
Elastic potential energy = 1/2 x spring constant x extension(squared)
What is the gravitatinal potential energy store of an object?
It relates to how high the object is above the earths surface - the higher it is the more gravitatinal potential store
How would we calculate the amount of energy in the gravitatinal potential store of an object?
GPE = mass x gravitatinal field strength x height
What is the value of the gravitatinal field strength on the earth and the moon?
Earth: g = 9.8N/kg
Moon: g = 1.6N/kg
What is power?
Power is a rate of transfereing energy, also considered as the rate of doing work
How would we calculate the power of an energy transfer?
power = work done (over time) = energy transfered(over time)
How would we define a Watt?
1 Watt is equal to a transfer of 1 joule per second
What does it mean if a kettle has 3kW rating?
The kettle transfers 3000J of energy to the thermal store of the water in it per second, the kettle alos does 3000J of work to the water in it every second
What is the law of conservation of energy?
How do we apply this law?
Energy cannot be created or destoryed, only stored and transfered, the total energy output from a device is equal to the total energy input.
