Work, Power, and Energy Flashcards
factors affecting work done
- magnitude of force applied
- displacement produced by the force
(3. angle between force and displacement)
amount of work done is equal to?
the product of the force applied on it and the displacement of the point of application of force, in the direction of force
work is scalar/vector
scalar
if a force displaces a body in direction other than direction of force, amount of work done can be determined by…
- finding the component of displacement along the force
- finding the component of force along the displacement
Special cases for work done
- if displacement is in the direction of force, work done is positive
- when displacement is normal to the direction of force, work done is 0.
- if displacement is in a direction opposite to force, work done is negative
work done by the force of gravity
work done by the force of gravity is the same whether the body comes down from a certain height using stairs or a slope or lift. if the body goes up, work done is negative
define 1 joule
1 joule of work is said to be done when a force of 1 newton displaces a body through a distance of 1 meter in its own direction
CGS unit of work
1 erg= 1 dyne * 1 cm
1 joule is how many erg
1 joule= 10^7 erg
define power
the rate of doing work (scalar)
power depends on
- amount of work done by the source
- time taken by the source to do said work
power is also equal to
force * average speed
SI and CGS unit of power
watt (W)
erg per second
define 1 watt
if 1 joule of work is done in 1 second, power spent is 1 watt
1 watt is how many erg per sec
1 W = 10^7 erg per second
1 HP is how many watts
1 HP= 746 W= 0.746 kW
define energy
the capacity of a body to do work (scalar)
when is there no transfer of energy
when a body is acted upon by a force normal to the direction of displacement
units of energy
SI: joule
CGS: erg
bigger units: watt hour. kilowatt hour
for heat energy: calorie
Electron volt
define 1 Wh
1 watt hour is the energy spent by a source of power 1 W in 1 hr
define 1 calorie
1 calorie is the heat energy required to raise the temperature of 1 g of water by 1 degree C
1 calorie is how many J
1 cal= 4.18 J
1 J= 0.24 cal
what is electron volt
the energy transfer in case of atomic particles is very small, so it is measured in electron volt eV
define 1 eV
1 eV is the energy gained by an electron when it is accelerated through a potential difference of 1 V
how many joules is 1 eV
1 eV= 1.6 * 10^-19 J
define potential energy
the energy possessed by a body at rest due to its position or size and shape is called potential energy
kinds of potential energy
- gravitational potential energy (negative)
- elastic potential energy
gravitational PE of a body at a point
work done by force of attraction of the earth in getting that body from infinity to that point.
OR
the amount of work done in lifting that body at a height against force of gravity
define kinetic energy
the energy possessed by a body due to its state of motione
expression of KE
the KE possessed by a moving body is equal to the amount of work which the moving body is capable of doing before coming to rest.
KE and momentum are related as
KE= p^2/ 2m
work-energy theorem
the increase in kinetic energy of a moving body is equal to the work done by a force acting in the direction of the moving body.
three forms of KE
- translational (straight line)
- rotational (rotating about an axis)
- vibrational (to and fro from a mean position)
forms of energy
- solar
- heat
- hydro
- light
- chemical
- electrical
- mechanical
- nuclear
- wind
define light energy
it is a form of energy in the presence of which other objects are seen
define electrical energy
when two dry bodies are rubbed together, they get charged due to the movement of free electrons from one body to the other body.
define nuclear energy
the energy released due to loss in mass during the processes of nuclear fission and fusion, is called nuclear energy.
define geothermal energy
the energy released in nuclear disintegrations in the interior of earth, gets stored deep inside and is called geothermal energy.
principle of conservation of energy
energy can neither be created nor be destroyed. it only changes from one form to another.
