module 1 Flashcards
What are the energy stores?
thermal, kenetic, gravitational potentia, elastic potential,chemical, magnetic, electrostatic, neulear.
What is a system and what happens when they change
a single object, energy is transfered.
How does a system change?
it can be transferred into or away from the system between different objects in a system or between different objects in a system or between different types of energy stores
What are closed systems?
Systems where neither matter nor energy can enter or leave. The net change in teh total energy of a closed system is always zero.
In a boiling kettle what is the system? What energy store is is transfered into?
Water, water heating element and water are two-object system, thermal energy store.
How does energy transfer in kettle?
electrical to thermal energy store of heating element. Then by heating to water’s thermal energy store.
What does work done mean?
energy transfered
What can work done be compleated by?
electric flow, by a force moving on object
What is the first stage of someone throwing a ball in the air?
initial force exerted by person throws ball in air. Energy transferes from chemical energy store in arm to kinetic energy store of ball and arm
What is the second stage of a ball in air?
ball dropping accelerates from height by gravity, gravitational force does work. Energy transferes from ball’s gravitational potential energy store to its kenetic energy store.
How do energy and forces act on cars?
friction between car’s brakes and its wheel does work as it slows down. Energy transferes from wheel’s kinetic energy store to thermal store of its surroundings.
What happens in a car crash?
contact force between car and object does work, transfer from car kentic to other energy stores, some energy might be transfered by sound waves.
What are the 3 most common energy stores?
kenetic, gravitation potential, elastic potential
What does everything moving have? What happens with speed?
Kenetic energy store, accelerate- energy transfered to this store. Energy transfered away when it slows.
What does kinetic energy store depend on?
Mass and speed,Greater mass and faster the speed more energy in the kinetic energy store.
What is the formula for kinetic energy?
E(k)=1/2MVsquared m=mass kg v=speed m/s squared. E(k=(j)
What does lifting an objects gravitational field require?
work, causes transfer of energy to gravitational potential energy. Higher lifted more energy is transferred.
What does energy in gravitatial potential depend on?
mass, height, and strength
What is the equation for gravitational potential energy?
E(p)=mgh m=mass kg g= gravitational field strength (N/kg) h= height metres e(p)= (j)
What happens when an object falls?
gravitational potential energy store transfers to kenetic energy store. If no air resistance energy lost from gravitational potential energy =energy gained from kinetic energy store.
What happens with air resistence?
energy is transfered to other energy stores e.g.thermal energy stores of the object and surroundings
What is elastic potential energy caused by?
Squashing or streaching an object so long as limit of proportionality hasn’t been exceeded.
What is the equation for elastic potential energy?
E(e)=1/2ke squared E(e)=(j) k=spring constant (N/m) e= extension (m)
Materials need different amounts of heat energy to warm up than others. What do materials that gain lots of heat do?
Transfer lots of energy when they cool down. They ‘store a lot of energy’.
What is specific heat capacity
The amount of energy need to raise the temperature of 1kg of a substance by 1 degree celcius.
What do you need to do to measure the specific heat capacity of a metal?
Get a block of a material with 2 holes (for a heater and thermometer to go into).
Why do you measure the mass of the block and wrap it in an insulating layer?
to reduce the energy transferred from the block to the surroundings. Then insert thermometer and heater.
What do you do after measuring the initial temperature of the block?
set the potential difference of the power supply to 10V. Turn on power supply and start stop watch.
What happens after you turn on the power supply?
the current in circuit does work on heater, transferring energy electrically from power supply to heater’s thermal energy store. Energy then transferred to material’s thermal energy store by heating. Increasing material’s temperature.
What do you do as the block is heating up?
take readings of temperature and current every minute for 10 minutes. Should find current doesn’t change as block heats up.
What should you do once you have collected your readings?
turn off power supply. using current and potential difference of power supply calculate the power supplied to heater using P=VI
What do you do with the equation P=VI
calculate how much energy has been transferred by the heater at time of each temperature reading using E=Pt E= energy (j)t=time (seconds) since experiment began
What can you do if you assume all energy supplied to heater has been transferred to block?
Plot graph of transferred energy to thermal energy store of block against temperature. Should have curve at beginning and then straight line.
What is the equation for specific heat capacity?
Change in E=MC change in temperature change. e= thermal energy (j) m= mass (kg) c = specific heat capacity (j/kg degrees Celsius).
How do you find the gradient?
change in temperature change divided by change in energy. Using equation for specific capacity equation, use equation 1/(gradient *mass of block) to find specific heat capacity.
Why repeat with other materials?
to compare specific heat capacity.
What is the example as a phone for conservation of energy and power?
useful energy transferred fro chemical store of battery. Some dissipated and transferred. to thermal store
What is the example for a flask for conservation of energy and power?
cold spoon dropped in to sealed flask. Energy transferred from thermal energy store of soup to useless thermal energy store of spoon. Energy transferred within system no energy lost- net charge in energy = 0.
What is power?
Rate of transfer or rate of doing work.
What does 1 watt equal?
1 joule of energy transferred per second.