How was the positron discovered?
A) By allowing electrons to collide in a particle accelerator.
B) By observing the cloud chamber tracks of high energy gamma rays as they created positron-electron pairs.
C) By observing the cloud chamber tracks of cosmic rays as they passed through a metal plate.
D) By creating them in very high energy collisions of heavy nuclei such as gold nuclei.
E) By allowing protons to collide in a particle accelerator.
C
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A tennis ball bounces off a brick wall. Which of the following is true?
A. The momentum of the ball is conserved in this process B. If the collision is elastic, then the ball's velocity does not change in this process C. The total momentum of the ball, wall, and Earth is conserved in this process D. None of these choices are true
A cloud fragment too small to collapse into a main sequence star becomes a
A) pulsar. B) planet of another star. C) T-Tauri object. D) brown dwarf. E) white dwarf.
Which of the following media cannot support longitudinal waves?
a. aluminum c. string b. air d. water
Steel blocks A and B, which have equal masses, are at TA = 300 °C and TB = 400 °C. Block C, with mC = 2mA, is at TC = 350 °C. Blocks A and B are placed in contact, isolated, and allowed to come into equilibrium. Then they are placed in contact with block C. At that instant,
a. TA = TB < TC. b. TA = TB = TC. c. TA = TB > TC. d. TA + TB = TC. e. TA - TB = TC.