Work, Power and Efficiency (Chapter P1) Flashcards
How is work done?
Work is done when a force is applied and an object is moved a distance. This transfers energy.
What is the equation for work done
Work done = force x distance
How would we define a joule?
1 Joule is the energy transferred when a force of 1 N causes a displacement of 1 m
What is the kinetic energy store of an object?
The kinetic store of an object relates to its motion. The faster an object moves, the more energy it has in its kinetic store.
A moving object also has mass and if a larger mass travels at the same speed it would have more energy in its kinetic store.
What is the equation for kinetic energy
= 0.5 x mass x velocity squared
What is the elastic potential energy store of an object?
The elastic potential store of an object relates to how stretched it is. The more stretched (extended) it is, the more energy it has in its elastic store.
What is the equation for elastic potential
= 0.5 x spring constant x extension squared
What is the gravitational potential energy store of an object?
The gravitational potential store of an object relates to how high above the Earth’s surface it is. The higher it is, the more energy it has in its gravitational potential store.
What is the equation for gravitational potential energy
= mass x gravitational field strength x height
What is the value of the gravitational field strength on the Earth and the Moon?
Earth: g = 9.8 N/kg
Moon: g = 1.6 N/kg
What is power?
Power is the rate of transferring energy, also considered as the rate of doing work.
What are the equations for power
= work done / time
= energy tranferred / 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 a 3 kW rating?
This kettle transfers 3000 J of energy to the thermal store of the water in it per second.
This kettle does 3000 J of work to the water in it every second.
What is the law of conservation of energy?
Energy cannot be created or destroyed, only stored and transferred.
