A strip of fur is rubbed against a hard rubber rod. The rod thereby acquires a negative charge because
A. rubbing caused electrons to move from the fur to the rod.
B. friction caused protons to be removed from the rod.
C. electrons from the air molecules are transferred to the rod.
D. frictional forces create electrons.
Answer: A
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Of the two colors shown in the image above, the pink colored nebula is the least common
a. True
b. False
Which of the following protogalactic clouds is most likely to form an elliptical galaxy?
A) a very low-density cloud with very little angular momentum B) a dense cloud with very little angular momentum C) a low-density cloud with quite a bit of angular momentum D) a very massive cloud with any density and a lot of angular momentum
Carbon-14 Dating: An archaeologist finds the 14C in a sample of 2.10 g of material to be decaying at 107 Bq. A modern 1.00-g sample of the same material decays at 151 Bq,and assume this rate has also held in the past. The half-life of 14C is 5730 years. How old is the sample?
A. 8980 years B. 6230 years C. 17,000 years D. 8530 years
An engine is designed to obtain energy from the temperature gradient of the ocean. What is the thermodynamic efficiency of such an engine if the temperature of the surface of the water is 59°F (15°C) and the temperature well below the surface is 41°F (5°C)?
a. 3.5% b. 67% c. 31% d. 17% e. 96%