Forces And Energy Flashcards
Define a force
A push or pull caused by it interacting with another object
What are the contact forces?
- friction
- lift
- thrust
- upthrust
- drag
- NCF
- tension
What are the non contact forces?
- weight
- magnetism
- electrostatic
What does normal mean
At a right angle
What is the unit of force and the symbol for force?
Newton (N)
F
What is weight measured in and the symbol for weight
Newtons, N
W
What is mass measured in and the symbol for mass?
Kilograms, Kg
m
What is gravitational field strength measured in and the symbol for gravitational field strength
Newtons per Kilogram (N/Kg)
g
What is the equation for weight?
W = mg
What is the difference between something being elastically seformed and inelastically deformed?
- elastically if it goes back to original shape after force is removed
- converse for inelastically
What is hooke’s law?
Shows extension of spring, elasticity.
Only true up to limit of proportionality
What is the symbol for extension and what is it’s unit?
e
Metres, m
What is the symbol for spring constant and its unit?
k
Newtons per meter N/m
Define energy
A measure of the ability to do work
What does conservation of energy state?
Energy cannot be created or destroyed, only transferred from one store to another
What are the 8 energy stores?
Kinetic
Chemical
Thermal
Gravitational potential
Elastic potential
Nuclear
Magnetic
Electrostatic
What are the 4 energy pathways?
Can be transferred:
Mechanically
Electrically
By heating
By radiation
What is work done?
The energy transferred when a force moves an object through a distance
What is the symbol for distance moved and its unit?
s
Metres, m
What is the symbol for work done and its unit?
W
Joules, J
What is the equation for work done?
W=Fs
What is the symbol for energy in the gravitational potential store and its units?
Eg
Joules, J
What is the symbol for height and its units?
h
Metres, m
What is the equation for energy in the gravitational potential store?
Eg = mgh
What is the symbol for energy in the kinetic store and its units?
Ek
Joules, J
What is the symbol for velocity and its units?
v
Metres per second, m/s
What is the equation for energy in the kinetic store?
mv²
Ek = ———
2
What is the symbol for energy in the elastic potential store and its units?
Ee
Equation for energy in the elastic potential store?
ke²
Ee = —-
2
What is the symbol for power and its units?
P
Watts, W
What is the symbol for energy transferred and its units?
E
Joules, J
What is the symbol for time and its units?
t
Seconds, S
Equation for power?
E
P = –
t
What is one watt equivalent to?
One joule per second 1J/s
What is useful and wasted energy transfer?
Useful transfer is to the desired store
Wasted is transferred to the undesired store
What is the equation for efficiency?
Useful energy transf
Efficiency= —————————-
Total energy input
What does a sankey diagram look like?
———-\
———-/
\
\
\ \
\ \
— —–
\ /
\ /
\ ________/
How to reduce unwanted energy transfers?
Use insulation (poor heat conductors)
Double glazing/cavity walls
Lubrication to reduce friction
What is conduction?
Energy transfer whereby vibrating particles transfer energy to neighbouring particles
Occurs in all states of matter
What is covection?
When fluids (liquds and gases) are heated, particles move faster and space between them increases, becoming less dense, so rise to sureface, cool becoming more dense, then sink. This movement is convection
What is thermal conductivity?
A measure if the rate a material transfers thermal energy
What does non renewable mean?
A resource that is not being replaced as fast as it is being used up, will eventually run out
Examples of fossil fuels
Coal, oil, natural gas
Advantages of of coal and gas burning power stations?
Very reliable
We already have the infrastructure
Disadvantages of of coal and gas burning power stations?
Releases CO², a greenhouse gas, causing global warming
Non-renewable, will run out
Examples of renewable energy
- wind
- solar
- hydroelectric
- tidal
- geothermal
- biomass
- waves
Pros and cons of wind energy?
- renewable energy source
- doesn’t release CO²
- flexible location
- unreliable, energy production fluctuates with wind speeds
Pros and cons of solar energy?
- renewable energy source
- doesn’t release CO²
- flexible location
- unreliable due to day-night cycle and weather fluctuations
Pros and cons of hydroelectric energy?
- renewable energy source
- doesn’t release CO²
- fixed location
- can be unreliable in case of drought
