Who first calibrated the Cepheid variable stars for use in determining distance?
a. Henrietta Leavitt
b. Edwin Hubble
c. John Glenn
d. Carl Sagan
e. Harlow Shapley
A
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Exhibit 13-1
Two blocks of masses m1 and m2 are connected by a light cord that passes over a pulley of mass M, as shown. Block m2 slides on a frictionless horizontal surface. The blocks and pulley are initially at rest. When m1 is released, the blocks accelerate and the pulley rotates.
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Use this exhibit to answer the following question(s).
Refer to . The total angular momentum of the system of the two blocks and the pulley relative to the axis of rotation of the pulley is
a.
proportional to the radius of the pulley.
b.
proportional to the speed of the blocks.
c.
proportional to the length of the string.
d.
to all of the above.
e.
only to (a) and (b) above.
A typical white dwarf is
A) as massive as the Sun but only about as large in size as Earth. B) as large in diameter as the Sun but only about as massive as Earth. C) about the same size and mass as the Sun but much hotter. D) as massive as the Sun but only about as large in size as Jupiter.
What is the activation energy?
A) the minimum amount of energy to break the bonds in reactants B) the amount of energy required to activate a phase change C) the energy difference between the reactants and the products D) the amount of energy required to separate reactants from the products E) the hill
A dime is 1.8 cm in diameter. At what distance from your eye would you have to hold a dime so that it has the same angular diameter as the full moon
a. 2 m b. 2 cm c. 2 km d. 2 inches e. 2 ft