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GUPPESS

GUPPESS. Problem solving approach G iven U nknowns P icture P rinciple E quation(s) (Governing) S olve (Algebra first!) S ubstitute (given values). Example.

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GUPPESS

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  1. GUPPESS • Problem solving approach • Given • Unknowns • Picture • Principle • Equation(s) (Governing) • Solve (Algebra first!) • Substitute (given values)

  2. Example • A sample of an ideal gas is held at 110 kPa within 15 liters volume. It’s temperature is 300o Kelvin. How many moles of the gas are in the sample?

  3. Given • What quantities are provided in the problem statement with a value? • Pressure = 110 kPa • Volume = 15 Liters • Temperature = 300 Kelvin

  4. Unknowns • Quantity of gas, number of moles.

  5. Picture

  6. Principle • What is the principle you can use to describe what situation is portrayed? • Ideal Gas Behavior

  7. Equation • What equation do you know, or you can find, that quantifies a relationship between the givens and unknowns? • Ideal gas law • PV=nRT • P=Pressure, V=volume, n=number of moles, R=ideal gas constant, T= temperature in degrees Kelvin

  8. Solve • Algebra first • you’ll make less math/calculator mistakes • you can retrace your work after to double check it. • PV=nRT; n=PV/RT

  9. Substitute • Givens explicitly provided in the problem statement, and some values, such as constants that you may need to look up.

  10. May need to convert! • R=0.08206 (Latm/mol K)(101.3 kPa/atm) =8.31 kPaL/mol K

  11. Kinematics Equations • v = vo + at • Dx = vot +½ at2 • v2 = vo2 + 2aDx • Dx = ½ (vo+ v)t v=velocity a=acceleration(constant) x=position Dx=change in position t=time subscript 0 means initital

  12. Now you try • A block slides down a ramp. At a certain point its velocity is 5.0 cm/s, after sliding 30 more cm, its velocity has increased to 15 cm/sec. Assuming uniform acceleration, what is the value of the acceleration?

  13. Given • What quantities are provided in the problem statement with a value? • x0 = 10 cm • Dx= 30 cm • vo=5.0 cm/sec=0.05m/s • vf=15 cm/sec=0.15m/s

  14. Unknowns • Acceleration down ramp

  15. Picture

  16. Principle • What is the principle you can use to describe the situation as portrayed? • Kinematics, motion in one dimension

  17. Equation • Pick one that has your knowns and the quantity you need to find v2 = vo2 + 2aDx

  18. Solve • Algebra first • you’ll make less math/calculator mistakes • you can retrace your work after to double check it. v2 = vo2 + 2aDx; a=(v2-v02)/2Dx

  19. Substitute • Givens explicitly provided in the problem statement, and some values, such as constants that you may need to look up.

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