Download Work Power and Energy 0910

Work, Power &
Energy
I. Energy
A.Energy is…
II. Kinetic Energy
A.The energy of motion.
Kinetic Energy depends
on…
B.Kinetic energy (KE) –
KE = ½
2
mv
III.Potential Energy
A.Stored energy due to
an objects state or
position.
The object has the
potential to do work.
Potential Energy depends
on…
B.Two kinds of PE…
1.Gravitational PE
potential energy created
by raising an object
above a reference point
PEg = weight x height
PEg = (mg)h
A
B
C
D
PEg depends on the reference point
or zero level
2.Elastic PE
potential energy created
by stretching a spring or
other elastic material
IV.Work
A.Work is done on an
object when…
B.Work –
W = Fd
(1J = 1N*1m)
J – Joule
Force and Distance cannot
be perpendicular
Fa
Ff
C.Total work equals total
force times the distance.
Wnet = Fnetd
V.‘+’ and ‘-’ Work
A.Work is a scalar
quantity, but it can still
be negative or positive
VI.Work and Energy
A.Doing work on an
object is a transfer of
energy
B.Work-energy theorem whenever work is done
energy changes
Wnet = ΔKE
-orFnetd = ΔKE
• Speed Stacking
• http://www.youtube.com/watch?v=JUYYs1
rDWsc
VII.Power
A.Power is...
B.Power – a quantity
that measures the rate
at which work is done
P = W/t
(1W = 1J/1s)
W – Watt
C.Units of power:
SI Unit is Watt (W)
English Unit is
horsepower (hp)
1 hp = 746 W
hp is donkey power
VIII.Conservation of E
A.Law of Conservation of E
–the total amount of
energy never changes
Total Energy initial
= Total Energy final
C.Mechanical Energy
(ME) – the sum of
kinetic energy and all
forms of potential
energy
D.Mechanical energy is
conserved when there
is no friction
Total MEi = Total MEf
KEi + PEi = KEf + PEf