# FNT9 - PE total KE total E total E bond E thermal(Remember...

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Physics 7A Exit Handout from DLM 09 DLM09 FNTs 3.1-8) Look at a graph of the pair-wise potential. Calculate the magnitude of the force at r = 1.4 σ . Assume ε = 5 x 10 -21 J, and σ = 1 x 10 -10 m. 3.1-9) Can a pair of bound atoms be a distance r = r 0 apart? Explain. Can a pair of unbound atoms be a distance r = r 0 apart? Explain 3.1-10) With respect to the plot of the pair-wise potential, what is the meaning of the following quantities: r 0 , r max , r min ? How are they different from or similar to “ r ”? How does one determine specific values of r min and r max ? 3.1-11) With respect to any oscillating system, what is the difference between Δ PE, PE, and PE AVERAGE ? 3.2-2a) Consider a system comprised of three identical particles whose pair wise interactions are governed by the pair wise potential energy shown on the plot to the right. The three particles are shown below, sitting at rest in their equilibrium positions, with no kinetic energy. ( r 0 = 1.0 angstrom) Determine the following for the situation described above:
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Unformatted text preview: PE total , KE total , E total , E bond , E thermal . (Remember that E total can be expressed as either a sum of PE and KE, or as a sum of the macroscopic energy systems E bond and E thermal , i.e., E total = PE + KE = E bond + E thermal ) 3.2-2b) After an amount of energy is added to the system, the three particles begin to oscillate. At a particular point in time the three particles are momentarily at rest , as shown below. i) Have any bonds been broken? What does you answer imply about E bond ? ii) Determine the following: PE total , KE total , E total , E bond , E thermal . r = r r = r r = 1.5 r r = 1.25 r 3.2-2c) For the amount of total energy in part ( b ), which of the 5 values that you found in part ( b, ii ) are constant in time? Explain . 3.2-2d) For the particular configuration of the three particles in part ( b ) the thermal energy is all PE. Will that be true at all points in time for that amount of total energy? Explain ....
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## This note was uploaded on 05/12/2010 for the course PHY 7 taught by Professor Staff during the Spring '08 term at UC Davis.

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