Energy Flashcards
Force applied and extension of springs relationship
They are directly proportional to each other but there is a limit of proportionality
What happens after you reach the limit of proportionality to the spring
The spring will not return to its original length
Law of conservation of energy
Energy can be transferred usefully, stored or dissipated but it cannot be created or destroyed
What is a system
A group of objects
friction acts on a pendulum as it passes through the air what is the result of this
What happens to the pendulums movement
(4)
The friction causes energy to be transferred to thermal energy
air around the fixed point where the pendulum is hanging from gets gradually warmer
These stores of thermal energy are less useful. The energy has been dissipated (wasted). This will cause the pendulums to gradually swing with less energy and eventually stop.
How could we reduce the loss of energy by friction by a pendulum
Lubricant oil or removing the air particles.
Describe the transfers of energy when a bungee jumper jumps
(6)
At the start of the jump, all of the energy in the system is in the store of GPE
As the jumper falls the GPE store converts into KE store
When the bungee rope just starts to tighten, the kinetic energy store is now at its maximum
When the rope is fully extended the KE store is 0 because the jumper is no longer extending all the energy has been transferred into EPE store. The bungee jump then recoils and is transferred from the EPE store back to the KE store.
As the jumper goes up the KE store would be transferred back into GPE store.
At the top all of the energy is now in the GPE store
Why would a bungee jumper not go back into the same original position as they jumped off (3)
This is because the energy is dissipated as thermal energy. Due to friction with air particles. It is also due to stretching effects in the bungee rope which is not fully elastic.
Work is done when?
Energy is transferred from one store to another
Mechanical work meaning
Using a force to move an object
Work done equation
Force * distance
How do brakes work
The brake presses against the wheel
This creates friction between the brake and the wheel
The KE energy store of a car is transferred to thermal energy store in the brakes.
The temperature of the brake increases and the car slows down
Factors that affect the cooling of a building
The high the thermal conductivity of a material, the high the rate of the energy transfer by conduction across that material.
What are modern houses walls built of
External brick and internal breezeblock and between the walls there is a cavity.
Builders pack the cavity with insulating material which has very low thermal conductivity.
Single glazed windows property
High thermal conductivity
Double glazed thermal conductivity
Low thermal conductivity
Loft insulation thermal conductivity
Has a low thermal conductivity reducing the rate of which thermal energy transfers through
How should a UK house be built and why
Construct the building with a low thermal conductivity
Build the house with thick walls as this also reduces the rate of thermal energy transfer
Practical specific heat capacity
step 1 and 2
- Place a beaker on a balance and press zero
- Now add oil to the beaker and record the mass of the oil
Practical specific heat capacity
step 3 and 4
Place a thermometer and an immersion heater into the oil
Read the starting temperature of the oil
Practical specific heat capacity
step 5 and 6
Wrap the beaker in insulating foam to reduce thermal energy transfer to the surroundings
Connect a joule meter and to the immersion heater
Practical specific heat capacity
step 7, 8 and 9
Wait for 30 minutes
Read the total number of joules of energy that passed into the immersion heater
and read the final temperature of the oil
Practical specific heat capacity step 10
Use the data you have gathered to find the specific heat capacity
(fix the problem practical) not all thermal energy passing into the oil
Ensure that immersion heater is full submerged
(fix the problem practical) Thermal energy passing out the beaker into the air
Use an insulator with a lower thermal conductivity
(fix the problem practical) Incorrect reading of the thermometer
Use an electronic temperature probe.
(fix the problem practical) Thermal energy not being spread through the oil
Stir the oil
Thermal insulation practical step 1 and 2
First we place a small beaker inside a larger beaker
We then use a kettle to boil some water.
Thermal insulation practical step 3 and 4
Next we transfer 80 cm^3 of the hot water into the small beaker
We then use a piece of cardboard as a lid for the large beaker and the lid must have a hole to insert a thermometer
Thermal insulation practical step 5 and 6
Next we place a thermometer through hole in a cardboard lid
The bulb of the thermometer must be in the hot water
