work power and energy Flashcards
energy is a vector quantity
true or false
false
energy is needed to do —–
mechanical work
energy conversions occur during
work done
energy is measured in
joules
formula of energy
e=mc2
energy can be stored as
chemical energy
elastic energy
potential energy
chemical energy used in
cells
solar energy used in
solar panels
nuclear energy used in
atomic bomb
potential energy (definition)
energy due to change in position of an object
kinetic energy (definition)
energy due to motion of an object
difference between kinetic and potential energy
kinetic energy is the energy due to its motion
potential energy is a stored form of energy due to its size and shape of the object
examples of kinetic energy
winds have kinetic energy
a sppining frisbee has kinetic energy
a rolling soccer ball also has kinetic energy
types of potential energy(also define them)
elastic potential energy: due to shape and size
gravitational potential energy : whenever there is a change in height of an object
the formula of kinetic energy and gravitational energy
KE: 1/2 MV2
GPE:MGH
definition of power(in terms of work done)
rate of doing work
definition of power ( in terms of energy)
rate of transfer of energy
formula of power
energy/time
power measured in
watts
definition of work done
Work done by a constant force on an object is the product of force and distance made by the direction of force
formula of work done
force multiplied by direction of force
unit of work done
NM
work done is not done when
work is not done when the object doesn’t move in the direction of the force
why does energy has the same unit as work done
because work done is equal to energy transformed
unit of work done
joules
principle of conversion of energy
energy can’t be made or destroyed but it changes forms
what is efficiency
it is the ratio of useful energy (work done) over input energy
formula of efficiency
output energy multiplied 100/input energy
efficiency is measured in
percentt
why does efficiency have no unit
because it is a ratio of two quantities
not all energy is transferred into useful energy part of it is transferred into
heat loss (fusion)
define renewable energy resources
renewable energy sources that can be replenished over a short period
define non renewable sources of energy
non-renewable sources of energy sources are energy sources that can’t be replenished over a short period
state examples of renewable sources of energy
solar energy, wind energy, hydro-energy, geothermal energy
state examples of renewable sources of energy
solar energy, wind energy, hydro-energy, geothermal energy
state examples of non-renewable sources of energy
coal, fossil fuels, nuclear fuels
explain solar energy
solar energy is the energy from the sun, the sun is a big ball of heat and light resulting from nuclear fission at its core. the nuclear reaction releases energy that travels outward to the surface of the sun
explain solar panels
solar panels absorb energy from the sun and converted it into electrical energy
most solar energy is collected through photovoltaic cells, typically made of silicon that acts as a semiconductor. the sun’s rays contain heat and radiation. when the rays hit the surface of the silicon cells, they cause a release of electrons that roam freely
in a solar panel heat energy from the sun turns into
electrical energy
in the block diagram of solar panel solar panel into
transformer
state the advantages of solar panel
low running cost
no major pollution
it is a renewable energy
state the disadvantages of solar panel
low efficiency
covers a large area
availability varies
amount of current produced by solar cells is usually too small to power devices that need a large amount of electricity
explain wind turbines
wind turbines convert the kinetic energy in the wind into mechanical power. the generator in the wind turbine can convert this mechanical into electricity
explain geothermal energy
geothermal energy is a type of renewable energy taken from the earth’s core. it comes from the heat generated during the original formation of the planet and the radioactive decay of materials. this thermal energy is stored in rocks and fluids in the center of the earth
explain hydroelectric energy
river and rainwater fill up a lake behind the dam. water rushes down from the lake and spins the turbine. the turbine connected to the generator, when the turbine rotates generator also rotates and produces electricity
explain fossil fuel/coal power station
in thermal energy stations, electricity is produced by burning non-renewable energy sources (like coal, and natural gas) as a fuel for the generation of heat energy by burning it. as the heat energy is transferred into the boiler the water in the boiler starts to boil and evaporate the high pressurized steam passes to the turbine and it rotates, as a result, the generator is turned on and produce electricity. once the steam has passed through the turbines, it is cooled and condensed(turned back into a liquid) so that it can be fed back to the boiler, and the process repeats
explain nuclear fission
nuclear fission is the splitting of a heavy nucleus into two lighter nuclei when the nucleus of an atom is bombarded with a neutron
the energy of the neutron causes the target nucleus to split into two (or more) nuclei that are larger than the parent nucleus, releasing a large amount of energy during the process
explain nuclear fission
nuclear fission is the splitting of a heavy nucleus into two lighter nuclei when the nucleus of an atom is bombarded with a neutron
the energy of the neutron causes the target nucleus to split into two (or more) nuclei that are lighter than the parent nucleus, releasing a large amount of energy during the process
explain nuclear fusion
nuclear fission is the combining of two lighter nuclei to form a heavier nucleus, releasing a vast amount of energy during this process.
nuclear fusion is believed to be the process by which energy is released by the sun. when the two hydrogens -2 nuclei moving at high speed collide, they can join together to produce a heavier nucleus(helium). a large amount of energy is released
explain the wind energy
wind power or wing energy describes the process by which the wind is used to generate mechanical power or electricity, wind turbines convert the kinetic energy in the wind into mechanical power
explain the wind energy
wind power or wing energy describes the process by which the wind is used to generate mechanical power or electricity, wind turbines convert the kinetic energy in the wind into mechanical power
