P1 - Conservation & dissipation of energy 1️⃣✅ Flashcards
What are the 4 types of energy transfers?
Mechanical working
Heating
Waves e.g. light/ sound by radiation
Electricity
What are all eight energy stores?
kinetic
magnetic
thermal
chemical
electrostatic
nuclear
elastic potential
gravitational potential
What is the equation for kinetic energy?
Ek = 0.5 x m x v2
m = mass kg
v2 = velocity squared m/s
What is the equation for elastic potential energy?
Ee = 0.5 x k x e2
k = spring constant N/m
e2 = extension squared m
What is the equation for gravitational potential energy?
Eg = m x g x h
m = mass kg
g = gravity 9.8
h = height m
What is the equation for weight?
W = m x g
m = mass kg
g = gravity 9.8
What is the equation for power?
P = e/t
e = energy J
t = time s
What is the unit for power?
Watts
What is the equation for work done?
W = f x s
W = work done J
f = force N
s = distance m
What is the equation for efficiency?
E = useful energy
——————-
total energy
Energy cannot be ___________ or __________
Energy cannot be created or destroyed
What is useful energy?
Useful energy is energy transferred to where it is wanted in a way that is wanted
What does lubrication do?
Lubrication is a way of reducing unwanted energy transfer due to friction
What does streamlining do?
Streamlining is a way of reducing unwanted energy transfer due to air resistance or drag
Efficiency is a _________ of how much ________ is ___________ _________
Efficiency is a measure of how much energy is transferred usefully
What is the unit of energy?
Joules
How do you get from joules to kilojoules?
divide by 1000
How do you get from kilojoules to joules?
multiply by 1000
Describe the energy transfer when a moving car slows down
the energy is transferred via mechanical working from the cars kinetic energy store to the thermal store of its breaks. Some energy is dissipated into the thermal store of the surroundings
What does dissipated mean?
When energy is dissipated, essentially it has been wasted and transferred to another, unwanted energy store
Describe the energy transfer when an electric kettle is used to heat water
the electric current in a kettle transfers energy to the heating element of the kettle - energy is then transferred from the heating elements of the kettle to the thermal energy store of the water
Describe the energy transfer when a falling apple hits the ground
the energy from the apples gravitational store is mechanically transferred to its kinetic store and from its kinetic store its dissipated into the surroundings by sound waves
What is a system?
An object or a group of objects
What is a closed system?
A closed system doesn’t transfer or receive any energy from the surroundings. The total energy in a closed system never changes.
