ch5 - work, energy and power Flashcards
‘doing work’
way of transferring energy from on object to another
‘doing work’
way of transferring energy from on object to another
doing work ON something =
transferring energy TO the thing
what is energy?
a calculated quantity that is conserved during any change, that which is transferred when a force does work
more work done =
. more force
. more distance
what is work done?
when a force displaces the body in the direction of the force, energy is transferred
work done formula
force * distance in the direction if the force
work done = energy transferred
work done component formula?
w = Fs cos O
what is gravitational potential energy?
the energy a body has due ti its position in a gravitational field
gpe formula
gpe = mgh
gpe = mgh derivation
energy transferred = work done
gpe = F * s
gpe = weight * h
gpe = mg * h
gpe = mgh
potential energy?
energy of an object because of its position or shape
forms of potential energy?
. gravitational - object in gravitational field
. electric - electrically charged of bject in an electrical field
. elastic - of a squashed, twisted, stretched objsct goes back to its original position
kinetic energy formula?
0.5mv²
ke formula derivation?
v² = 2as + 0
times both sides by 0.5m
0.5mv² = mas
0.5mv² = Fs
energy transferred = work done
more ke
more speed of motion of force
gpe and ke on a hill?
- top of hill, max gpe
- going downhill, gpe to ke
- bottom of hill, all gpe to ke, sound, heat
- going uphill, ke to gpe
percentage efficiency?
useful output / total input * 100%
sankey diagram
to show energy transfers
principle of conservation of energy
energy cannot be created or destroyed - only changed from one form to another
total energy before = total energy aft r
power?
rate at with the device does work per unit time
power formula
P = W/t
P = Fv
watt
one joule per second, unit of power
P = force * velocity derivation
work done = F * dist
W = F * v * t
P = W/t
P = Fvt/ t
P = Fv
average human power
116W
