unit 4 - energy
12/6/18
energy : the ability to do work ; the stuff that allows us to make changes
work : a transfer of energy
gravitational potential energy
*determined by height and mass
*determined by velocity and mass
*determined by stretch, elasity, and spring constant (k)
ENERGY IS ALWAYS CONSERVED
transferred energy
12/6/18
energy : the ability to do work ; the stuff that allows us to make changes
work : a transfer of energy
gravitational potential energy
*determined by height and mass
- Ug or Eg or GPE
- energy stored in the distance between the object and its source in a gravitational field
- measured by the amount of distance between between objects
*determined by velocity and mass
- Ke or Ek or KE
- energy stored in the motion of mass
- measured by the speed/velocity of an object
*determined by stretch, elasity, and spring constant (k)
- Us or Es or EPL
- energy stored in elastic force field. stored in distortion (expansion/stretch/compression) of an object
- measured by the amount of compression or stretch of an object
- Uint or Eint
- energy stored in the random motion on the molecular level of an object’s composition
- measured by the temp. of an object (not heat)
ENERGY IS ALWAYS CONSERVED
- energy can never be created nor destroyed. this means the total amount of energy will never change.
- Eintial = Efinal
transferred energy
- working (w) : by exerting a external push or pull on system
- heating (q) : a temp. difference between system and surroundings causes energy to transfer from warmer to cooler object (temp being average kinetic energy in object)
- radiating (r) : matter loses energy when radiating light, and gains energy when it absorbs light
- Eintial + w + q + r = Efinal
- you only add whatever gets added or subtracted during the energy transfers to the initial energy which will equal the final amount of energy once the transfers are complete
- a way to graph/represent the energy transfers that take place or don’t take place in a system
*they have the graph of initial energy on the far left then in the circle is where you define the system and show the energy transfers that take place and then the far right is a graph of what the final energy looks like after the transfers
*both initial and final graphs amount of energy should be equal (not necessarily same type of energy however)
*both initial and final graphs amount of energy should be equal (not necessarily same type of energy however)
*an example of a lol chart about a cup of coffee releasing heat
positive work (+)
equations/solving
external push or pull
W = F x X
W = Fll x d
*only care about the component of force in the direction of the displacement therefore...
force in the direction of displacement
W = Fdcos(theta)
W = Fll x d ( ll = parallel to distance you travel)
change in F = W = Fll x d = Fdcos(theta)
AREA UNDER A F v CHANGE IN X GRAPH IS = TO THE ENERGY TRANSFERRED THROUGH WORKING
elastic potential energy
W = Us
½ bh = Us
½ x Fs = Us *(Fs = -kx)
Us = ½ k x^2 *for hookean springs
gravitational potential energy
W = Ug
l x w = Ug
yFg = Ug
Ug = m g h
Ug = m g y *(h = y = height)
kinetic energy
W = KE
L X W = KE
XF = KE
X M A = KE
KE = 1/2 MV^2
energy transferred = area under a force displacement graph
positive work (+)
- when a transfer of energy occurs through positive working that means energy is transferred into our system.
- the total energy of the system will increase
- when a transfer of energy occurs through negative energy that means energy is transferred out of our system.
- the total energy of the system will decrease
equations/solving
external push or pull
W = F x X
W = Fll x d
*only care about the component of force in the direction of the displacement therefore...
force in the direction of displacement
W = Fdcos(theta)
W = Fll x d ( ll = parallel to distance you travel)
change in F = W = Fll x d = Fdcos(theta)
AREA UNDER A F v CHANGE IN X GRAPH IS = TO THE ENERGY TRANSFERRED THROUGH WORKING
elastic potential energy
W = Us
½ bh = Us
½ x Fs = Us *(Fs = -kx)
Us = ½ k x^2 *for hookean springs
gravitational potential energy
W = Ug
l x w = Ug
yFg = Ug
Ug = m g h
Ug = m g y *(h = y = height)
kinetic energy
W = KE
L X W = KE
XF = KE
X M A = KE
KE = 1/2 MV^2
energy transferred = area under a force displacement graph