Changes in Energy Stores (P1.1) Flashcards
(18 cards)
What are the 5 main energy stores that energy can be transferred into?
Chemical energy stores, Kinetic energy stores, Gravitational potential energy stores, Elastic potential energy stores and Thermal energy stores.
What are the 4 main energy transfers?
A force of a moving object, heating, light waves or sound waves and an electric current.
Describe energy put in each of the 5 main energy stores.
Chemical energy stores: Include fuels, foods, or the chemicals found in batteries. (The energy is transferred during chemical reactions).
Kinetic energy stores: Describes the energy an object has because it is moving.
Gravitational potential energy stores: Used to describe the energy stored in an object because of its position.
Elastic potential energy stores: Describes the energy stored in a object when you stretch or compress it.
Thermal energy stores: Describes the energy a substance has because of its temperature.
Define what a system is.
A system is a single object or a group of objects.
What happens when a system changes?
When a system changes, energy is transferred. It can be transferred into or away from the system, between different objects in the system or between different types of energy stores.
Define what closed systems are.
Closed systems are systems where neither matter nor energy can enter or leave. The net change (total change) in the total energy of a closed system is always zero.
State what the conservation of energy principle is.
Energy cannot be created or destroyed.
What is work done the equalled to?
Energy transferred.
State what the equation of work done is.
Work done (J) = force applied (N) x distance moved along the line of action of the force (meters, m)
State what equation is used for the change in objects gravitational potential energy store.
Change in objects gravitational potential energy store (J) = weight (N) x change of height (meters, m)
State what equation is used for finding the (change of) gravitational potential energy.
Gravitational potential energy (J) = mass (kg) x gravitational field strength (N/kg) x change of height (meters, m)
State what equation is used for finding the kinetic energy.
Kinetic energy (J) = 1/2 x mass (kg) x speed squared (m/s) squared
State what equation is used for finding the elastic potential energy.
Elastic potential energy (J) = 1/2 x spring constant (N/m) x extension squared (m) squared
Define what useful and dissipated energy is.
Useful energy is energy transferred to where it is wanted in the way that is wanted
Dissipated (wasted) energy is the energy that is not usefully transferred.
What is the equation for power?
Power = energy transferred divided by time
What is the equation for efficiency?
Efficiency is useful power output divided by total power input
What are three ways in which you can improve the efficiency of a device.
You can improve the efficiency of energy transfers by insulating the objects, applying lubricant on moving parts (to reduce friction and tightening loose parts (to also reduce friction and vibrations.)
Explain why no device can be more than 100% efficient.
No device can be more than 100% efficient, because you can never get more energy from a machine than you put into it.