How do scientists estimate how old the universe is?
A) They look up the answer in a book.
B) They measure how fast the Sun is losing energy, and how much energy it has to lose.
C) They measure the abundances of radioactive elements in meteorites, and use their half-lives to calculate the age.
D) They measure the speeds and distances of galaxies, and calculate the time it took for them to travel that distance.
E) They make a guess; no one really knows how old the universe is.
D
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Four equal negative point charges are located at the corners of a square, their positions in the xy-plane being (1,1), (?1,1), (?1,?1), (1,?1). The electric field on the x-axis at (1,0) points in the same direction as
A) i^ B) j^ C) -i^ D) -j^
Simple Harmonic Motion: A simple harmonic oscillator oscillates with frequency f when its amplitude is A. If the amplitude is now doubled to 2A, what is the new frequency?
A. 2f B. 4f C. f D. f/2 E. f/4
If a photon's frequency increases, its wavelength
A. will increase. B. will decrease. C. will not change.
A spherical balloon contains a positively charged particle at its center. True or false, as the balloon is inflated to a larger volume while the charged particle remains at the center, which of the following is true?
1.The electric potential at the surface of the balloon increases. 2.The magnitude of the electric field at the surface of the balloon increases. 3.The electric flux through the balloon remains the same. 4.none of these