P1 Conservation and Dissipation of Energy Flashcards
(33 cards)
Energy can be stored in a variety of different energy stores
How can it be transferred?
Energy can be transferred by heating, by waves, by an electrical current, or by a force when it moves an object
What happens to an object that falls and gains speed (energy stores)?
When an object falls and gains speed it’s gravitational potential decreases and its kenetic energy store increases.
What happens when an object hits a ground?
It’s kenetic energy store decreases and it’s transffered to sound waves and the thermal energy store in the sourrounding increases
Conservation of energy (and what does it apply to)?
Energy cannot be created or destroyed, at applies to all energy changes.
What’s a closed system
A system in which no energy tranfers out off or into the energy stores of the system.
What can happen to the energy store in a closed system?
Energy can transfer between the energy stores in a system, but the total energy within the system is always the same.
When is work done
Work is done on an object when a force makes the object move
Equation for work done
Energy transferred= work done
W= F x s (F is the force and s the distance moved)
Energy transfer: Work done to overcome friction
Thermal energy stores of the objects rubbing together and to the surrounding.
How could you alternate gravitaional potential energy
When an object moves up (increases) or moves down (decreases)
Why does the gravitational potential store increase when an object is lifted
Because when lifted there is work being done on it to overcome the gravitational force (work done)
How does the gravitational field strength differ from the Earth and the Moon
Earth’s is greater (stronger)
Equation: change of gravitational potential energy
Change Gravitational potential energy store= mass x gravitational field strength x change of hieght
Change Ep= m x g x change h
What does the kinetic energy of a moving object depend on
It’s speed and mass
Equation: kenetic energy store
Ek = 1/2 m x v squared
Joules, Kg, m/s
What is elastic potential energy
It’s energy in an elsatic object when work is done to it
Equation: elastic potential energy (in a spring)
Ee= 1/2 k x e squared k= Spring constant e= extension
Joules, N/m, m
What is useful energy
Energy in the place we want it and in the form we need it to be in.
What’s wasted energy
Energy that is not useful energy and created by an undersired pathway
What eventually happens to all wasted energy?
Transfers to the sourroundings, which become warmer
What happens to energy as it dissipates (spreads out)?
Gets less and less useful
Equation on the effciency of a device?
Useful energy transferred by the device/ total energy supplied to the device (x 100)
What is the max energy transfer
No more than 100% efficient
How do machines waste energy
Through friction by the moving parts, air resistance, electrical resistance and noise
