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20. An electron has been accelerated by a potential difference of 100 V. If its position is known to have an uncertainty of 1 nm, what is the percent uncertainty (ΔP/P) × 100% of the electron? (A) 1% (B) 8% (C) 10% (D) >>10% (E) 5%

19. Frank says that quantum mechanics does not apply to baseballs because they do not jump from quantum state to quantum state when being thrown. Francine agrees with him. She says that there is no uncertainty in a baseball's position or momentum. Are they correct, or not, and why? (A) They are correct because the first excited state of a baseball is at a higher energy that any baseball ever receives. Therefore, we cannot determine whether or not there is uncertainty in its position or momentum. (B) They are correct because the first excited state of a baseball is at a higher energy that any baseball ever receives. Therefore, its position and momentum are completely uncertain until it is caught. (C) They are wrong because the baseball goes through so many quantum states in being thrown that we cannot observe the transitions. The uncertainties in its position and momentum are too small to observe. (D) They are wrong because the baseball goes through so many quantum states in being thrown that we cannot observe the transitions. Because of the number of transitions its position and momentum are completely uncertain until it is caught. (E) Quantum mechanics states that they are correct as long as they do not make any observations, but wrong as soon as they begin to make observations.

18. A spaceship from another galaxy passes over the solar system directly above a radial line from the Sun to the Earth. (We measure that distance to be 1.5 × 10¹¹ m.) On Earth, the spaceship is observed to be traveling at a speed of 0.80c, for which γ = 5/3. As measured on Earth it takes the spaceship 625 seconds to travel from the Sun to Earth. When a scientist in the spaceship measures the Earth-sun distance and the time it takes her to travel that distance, she finds the results are, respectively, (A) 1.5 × 10¹¹ m; 625 s. (B) 9.0 × 10¹⁰ m; 625 s. (C) 9.0 × 10¹⁰ m; 375 s. (D) 2.5 × 10¹¹ m; 625 s. (E) 2.5 × 10¹¹ m; 1042 s.

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