Energy, Work And Power Flashcards
A snowball hitting a wall
Explain which store to which store energy is transferred
Kinetic energy into thermal energy of surroundings
A car driver braking in an emergency
Kinetic energy of moving car
To thermal energy of surroundings
Name the 8 energy stores
-kinetic energy
-chemical energy
-magnetic energy
-thermal/ internal energy
-nuclear energy
-electrostatic energy
-gravitational potential energy
-elastic potential energy
Name four ways that energy can be transferred
-mechanically
- electrically
-through heating
-through radiation
How much GPE does an object have before work is done on it?
0
What is the formula for calculating GPE
GPE= mass(kg) x gravitational field strength(N/Kg) x CHANGE in height(m)
What kind of energy do our muscles store
Chemical energy
Thermal energy is transferred from… to …
Higher temperatures
Lower tempertaure
Why is conduction more rapid in metals
Because they have delocalized electrons which are able to flow easily throughout the structure
Explain how heat is transferred through a kebab stick in terms of energy stores and energy transfers
Energy from thermal energy store of fire is transferred to kinetic energy store of particles in kebab
Kinetic Energy from most energy particles is transferred to other particles mechanically
Is copper a better conductor of heat of steel
Copper
Is air an water a conductor or insulator of heat
Insulator
Explain how woolen clothing allows you to keep warm
Air, an insulating substance gets trapped in fibers
Where body heats the air and stops you losing heat
Explain how an offshore breeze works at night
-water has a higher specific heat capacity than water so stays longer for warmer
- thus air above sea warms faster as particles above it gain kinetic energy
-so they begin to expand and rise, as cool air from the land replaces it
When a bathroom heater is turned on, name two reasons the heat reaches you so quickly
The infrared waves are traveling in a straight line
The reflector is specially shaped and is very shiny
How is it possible that we can receive light from the sun
Because Infared waves can travel through a vacuum
Explain how a heat sink prevents a transistor from over heating (or electrical device)
Transistor is connected to heat sink, where thermal energy is transferred through conduction to the heat sink.
The heat sink is Matt black and this is a good radiator of heat
It is also designed in such a way that air convection currents can carry the hot air away
Do shiny objects reflect or radiate heat
Reflect
Explain why a reflector(shiny material) emits less thermal energy than a radiator(black material)
Because reflectors reflect heat away whereas radiators absorb and emit heat energy
Complete the blanks
At lower temperatures, most thermal energy is radiated through …… waves which is….to human eye
But at higher temperatures, most thermal energy is radiated through….. waves which is …. To human eye
Infrared, invisible
Shorter wave lengths, visible(because object starts glowing)
Explain how aluminum foil prevents marathon runners from losing heat
Inner side is reflective and so reflects any heat back to their body
Outerside is a poor radiator so does no emit any heat back to surroundings
How can wind cause body temperatures to fall
Wind molecules come very close to face and warm molecules from face begin to be swept into atmosphere through forces convection
Why are copper kettles kept polished
So that they remain good reflectors and thus reduce heat loss
What is the statement that answers what energy does
Energy is the ability to do work(where work is equal to energy transfer)