1. In the ?ssion of 235U, the masses of the ?nal products are less than the mass of 235U. Does this make sense? What happens to the mass?
21. In the fusion of deuterium and tritium nuclei to produce a thermonuclear reaction, where does the kinetic energy that is produced come from?

2. Mary, the astronaut, wants to travel to the star system Alpha Centauri, which is 4.3 lightyears away. She wants to leave on her 30th birthday, travel to Alpha Centauri but not stop, and return in time for her wedding to Vladimir on her 35th birthday. What is most likely to happen?

(a) Vladimir is a lucky man, because he will marry Mary after she completes her journey.

(b) Mary will have to hustle to get in her wedding gown, and the wedding is likely to be watched by bil- lions of people.

(c) It is a certainty that Mary will not reach Alpha Centauri if she wants to marry Vladimir as scheduled.

(d) Mary does reach Alpha Centauri before her 35th birthday and sends a radio message to Vladimir from Alpha Centauri that she will be back on time. Vladimir is relieved to receive the message be- fore the wedding date.

3. A salesman driving a very fast car was arrested for driving through a traf?c light while it was red, according to a policeman parked near the traf?c light. The salesman said that the light was actually green to him, because it was Doppler shifted. Is he likely to be found innocent? Explain.