Consider a radioactive substance with a half-life of 10 years. If you start with 1 kilogram of this substance, after 20 years, ________ of the radioactive substance will remain.
A) 0.25 kilogram
B) none
C) 0.75 kilogram
D) 0.5 kilogram
A) 0.25 kilogram
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Two simple pendulums of equal length l = 0.45 m are suspended from the same point. The pendulum bobs are small solid steel spheres. The first bob is drawn back to make a 35° angle with the vertical, while the other one is left hanging at rest
If the first bob has a mass of 0.25 kg and the second has a mass of how high will the second bob rise above its initial position when struck elastically by the first bob after it is released? A) 2.7 cm B) 3.3 cm C) 4.4 cm D) 3.9 cm
The __________ binds quarks together
Fill in the blank(s) with correct word
The Doppler shift for electromagnetic radiation from distant galaxies moving toward the observer is called a:
a. vacuum shift. c. red shift. b. blue shift. d. black shift.
The surface of a protostar radiates energy while its core
A) shrinks and cools. B) shrinks and maintains a constant temperature. C) shrinks and heats. D) expands and cools.