Why does the Sun appear red at sunrise and sunset?
A. The Sun gets embarrassed when it's near the horizon.
B. We don't have a good explanation.
C. The Sun's temperature varies on a 12 hour cycle.
D. Light passes through more atmosphere and red light gets through, whereas blue light scatters
E. The sun is cooler at sunrise and sunset.
Ans: D. Light passes through more atmosphere and red light gets through, whereas blue light scatters
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Bert and Ernie are two friends of the same age. Bert visits a nearby star system on a spaceship that travels close to the speed of light while Ernie stays at home. Which of the following will be true on Bert's return to Earth?
A) Ernie will be younger than Bert B) Ernie will be older than Bert C) Bert and Ernie will still be the same age D) Ernie will not have been born
What is the proper abbreviation for ‘grams?'
a. g b. gms c. gm d. gr e. kg
What is the moderator of a nuclear reactor?
a. The control rods that halt a chain reaction if it is out of control. b. A substance that absorbs neutrons to keep the reaction in control. c. The material that slows down the neutrons to induce more chain reactions. d. The material that speeds up the neutrons to induce more chain reactions. e. The name for the fissionable material itself (usually uranium).
You throw a Frisbee of mass m and radius r so that it is spinning about a horizontal axis perpendicular to the plane of the Frisbee. Ignoring air resistance, the torque exerted about its center of mass by gravity is
A. 0. B. mgr. C. 2mgr. D. a function of the angular velocity. E. small at first, then increasing as the Frisbee loses the torque given it by your hand.