This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Version 100/ABCBA – Test #3 – Antoniewicz – (56445) 1 This printout should have 22 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. 001 10.0 points The potential energy U ( r ) between any two atoms, when given as a function of the dis tance between their centers, will have a form similar to the graph below. U ( r ) r E 3 E 2 E 1 For which possible total energy of the two atoms, as shown in the sketch, do the atoms behave most like a simple harmonic oscillator? 1. E 3 2. They behave like a SHO for any energy. 3. There is no energy for which the two atoms will behave in any way even vaguely like a SHO. 4. E 1 correct 5. E 2 Explanation: Since a SHO potential energy would be pro portional to ( r r ) 2 , where r is a constant, we would expect U ( r ) to be most like a SHM at the energy E 1 . Therefore, for the lowest energy, E 1 , the potential energy is most like that of a simple harmonic oscillator. 002 10.0 points The force due to a deflected cantilever beam can be modeled using a linear and cubic term, i.e. F beam = k 1 δ k 3 δ 3 where δ is the deflection at the end of the beam. What work must be done on the beam to deflect it by 16 cm if k 1 = 97 N / m and k 3 = 20000 N / m 3 ? 1. 2.92793 2. 17.2955 3. 4.5184 4. 3.10219 5. 16.6635 6. 7.15522 7. 5.6066 8. 5.7024 9. 25.9246 10. 20.3996 Correct answer: 4 . 5184 J. Explanation: The work done on the beam is given by W on beam = W by beam = Z δ max F beam d δ = Z δ max k 1 δ + k 3 δ 3 d δ = 1 2 k 1 δ 2 + 1 4 k 3 δ 4 δ max = 4 . 5184 J 003 10.0 points The figure shows a potential energy curve for the interaction of a two atom system. The horizontal line represents a bound state with constant K+U value. Version 100/ABCBA – Test #3 – Antoniewicz – (56445) 2 What is the minimum amount of energy (in units of eV) which must be supplied to cause the separation of two atoms? (Caution: be careful with the sign here.) 1. 0.2 correct 2.1.2 3.0.9 4.0.2 5. 1.3 6. 0.9 Explanation: The minimum amount of energy needed is to bring the system from present state where E i = ( K + U ) i = . 2 eV to the final state where E f = ( K + U ) f = 0. The energy principle is E f E i = W Δ E = W = E f E i = 0 ( . 2 eV) = 0 . 2 eV . 004 10.0 points The escape speed from an asteroid whose ra dius is 20 km is only 6 m / s. If you throw a rock away from the asteroid at a speed of 12 m / s, what will be its final speed? Use G = 6 . 7 × 10 11 N · m 2 / kg 2 . 1. 10.3923 2. 12.1244 3. 22.5167 4. 17.3205 5. 20.7846 6. 25.9808 7. 15.5885 8. 13.8564 9. 19.0526 10. 24.2487 Correct answer: 10 . 3923 m / s. Explanation: First use the escape speed to get the mass of the asteroid: v esc = r 2 GM R ⇒ M = 1 2 v 2 R G = 5 . 37313 × 10 15 kg ....
View
Full
Document
This note was uploaded on 11/17/2011 for the course PHY 303K taught by Professor Turner during the Fall '08 term at University of Texas at Austin.
 Fall '08
 Turner
 Energy, Potential Energy

Click to edit the document details