Flashcards in ⭐️Topic SP3 - Conservation Of Energy Deck (41)
What are the energy stores?
-elastic potential energy
-gravitational potential energy
Give some energy transfers
What is the law of conservation of energy?
Energy can’t be created or destroyed and is only transferred
What are the units of energy?
What are the energy stores and transfers in a breaking car?
Kinetic energy transferred by forces during breaking causing thermal energy to be stored in the brakes
What does a snakes diagram show?
Amount of energy transferred, width of the arrows represents the amount of energy in J
When does energy dissipate?
When transferred to its surroundings
How can friction be reduced?
By lubrication through gasses, oil or liquids
What energy transfers does friction cause?
By heating and is usually wasted energy
When you pedal a bike, how is wasted energy transferred to surroundings?
What number is efficiency given as?
Between 0 and 1 and the higher the efficiency the better efficient the machine is
How do you calculate efficiency?
Useful energy transferred / total energy supplied to the device
What increases the efficiency?
Reducing the amount of wasted energy
How can wasted energy be reduced?
Reducing friction in mechanical processes, finding ways all fuel going into an engine is burned
How can energy be transferred by heating?
Conduction, convection and radiation
What happens in conduction?
Vibrations are passed on between particles in a solid
What happens in convection?
Part of the fluid that’s warmer than the rest rises and sets up a convection current
What’s different about radiation in terms of transferring heat?
energy can be transferred through a vacuum
What is infrared radiation absorbed and emitted by?
Absorbed and emitted easily by dull and dark surfaces and is absorbed poorly by light and shiny surfaces
Name a good thermal conductor and why
A metal as energy can be easily transferred through it by heating
Why is air a good thermal insulator?
As when trapped, it doesn’t form convection currents so not much energy is transferred
how is rate of energy transferred through a material reduced?
-decreasing thermal conductivity
-decreasing temperature difference
How can you decrease the thermal conductivity if a house?
By building them with a cavity do less energy escape as it contains air between two walls which acts as an insulator to reduce the rate of energy transfer
How does a vacuum flask keep drinks hot or cold?
As where the liquid is encased in glass walls with a silver coating that poorly absorb and emit infrared radiation. There is then another wall with a vacuum gap between it and the liquid container to prevent energy transfer
When does an object have a store of GPE?
When it’s above the surface of the earth
What is the formula for change in GPE?
Change in GPE (J) = mass (kg) x gravitational field strength (N/kg) x change in vertical height (m)
What is gravitational field strength in earth?
9.8 N/kg but can be rounded to 10N/kg in calculations
What’s kinetic energy?
The energy stored in moving objects
How can you calculate kinetic energy?
Kinetic energy (J) = 1/2 x mass (kg) x speed^2 (m/s^2)