What happened to all of the quarks that existed freely during the particle era?
A) They froze out of the soup of particles at the end of the era.
B) They combined in groups to make protons, neutrons, and their antiparticles.
C) They evaporated.
D) They combined in groups to make electrons and neutrinos.
B
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You press a stick that has a varying cross-sectional area horizontally between the palms of your hands. The area of the stick pushing against your left palm is twice the area of the stick pushing against your right palm.The pressure on your left palm is __________ the pressure on your right palm
Fill in the blank(s) with correct word
A zero decibel sound level has zero amplitude
a. True b. False Indicate whether the statement is true or false
An atom that is excited
a. is also ionized. b. is an isotope. c. has had its electron moved to the lowest energy level. d. can emit a photon when the electron moves to a lower energy level. e. can emit a photon when the electron moves to a higher energy level.
Car A rear ends Car B, which has twice the mass of A, on an icy road at a speed low enough so that the collision is essentially elastic. Car B is stopped at a light when it is struck. Car A has mass m and speed v before the collision. After the collision
A. each car has half the momentum. B. car A stops and car B has momentum mv. C. car A stops and car B has momentum 2mv. D. the momentum of car B is four times as great in magnitude as that of car A. E. each car has half of the kinetic energy.