EPE – Calories- Law of Conservation of Energy and Work-Energy Theorem

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EPE – Calories- Law of Conservation of Energy and Work-Energy Theorem

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EPE – Calories- Law of Conservation of Energy and Work-Energy Theorem

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EPE – Calories-Law of Conservation of Energyand Work-Energy Theorem

Another type of PE is…Elastic Potential Energy( EPE)Energy stored in an obj. at its stretched or compressed state.Obj. will return to its original or relaxed length.

- EPE or Uel = ½ k x2
EPE - elastic potential energy, J

- k - spring constant- STIFFNESS, N/m
(indicates how easily a material stretches or compresses

‘higher k stiffer material’

- x – the distance the spring is stretched or compressed
from relaxed length ( x = ℓs - ℓr ) or ( x = ℓr - ℓc )

( ℓr = relaxed length )

( ℓs = stretched length ) or ( ℓc = compressed length )

- Work can’t be done w/out _____________.
- The unit for Energy is ______________.
- The UNIT of HEAT ENERGY is calorie.
- It is = to 4.18 J ( Note the small “c” )
- A calorie is the heat necessary to raise the temperature of 1 g of water 1°C.
- The UNIT for FOOD ENERGY is Calorie.
- (Note the Big “C” )
- 1 Calorie = 1000 calories

- Energy cannot be created nor destroyed, only changed to another __________.
- Same as the Law of Conservation of Mass
- Mass/ Matter in a closed syst. cannot be created nor destroyed only conserved.

The total energy of a closed,

isolated system is constant

KE1 + GPE1 + EPE1 = KE2 + GPE2 +EPE2

OR

½ mv12 + mgh1 + ½ kx12 = ½ mv2 2 + mgh2 + ½ kx2 2

OR

GPE(t)op + KE(t)op = GPE(b)ottom + KE(b)ottom

Work-Energy Theorem-KE

According to the Work-Energy theorem,

the work done on an object, by the net

force acting on it, is equal to the change

in kinetic energy of the body

Work = Δ KE

F*d = KEf – KEi

F*d = ½ m vf 2 – ½ m vi2

F*d = ½ m (vf2 – vi2)

- When work is done, potential energy can also be changed.