What is the force that keeps planets orbiting the Sun and moons orbiting planets?
a. weight
b. inertia
c. mass
d. gravity
Answer: d. gravity
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A beam of light P has twice the wavelength but the same intensity as beam Q. The number of photons that hit a given area in a given time when it is illuminated by beam P is (A) twice, (B) the same, or (C) one-half of the number that hit when the area is illuminated by beam Q?
A. Twice B. The Same C. One-half of the number that hit
Active galaxy radio lobes and jets contain magnetic fields
a. True b. False Indicate whether the statement is true or false
Dark energy accounts for what percent of the known energy in the universe?
A) 68% B) 24% C) 8% D) 94%
Which is a useful property of a prism?
A) internally reflects 100% of incident light B) changes directions of light in a variety of ways C) re-inverts images D) all the above E) none of the above