Two twin sisters, Gwen and Jackie, are both 20 years old in the year 2020. Jackie takes off on a round-trip to Vega, 25 light-years away. She travels at an average speed very close to the speed of light—say, 0.9999c
According to Gwen back on Earth, about how long does it take Jackie to reach Vega? A) about a month
B) about 10 years
C) about 25 years
D) about 100 years
C
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Nanoparticles are finding many applications including medicine, magnetic permanent memory, and high strength materials. Assume that a high strength nickel alloy is to be made out of nanoparticles, and that the size of the nanoparticles is a cube 10 nm on each side. Calculate the number of atoms in these particles in two ways.
(a) For face centered cubic nickel calculate the number of atoms using only the lattice parameter of 0.352 nm from Appendix B and (b) using the density of nickel and the atomic mass from Appendix B.
Low levels of ionizing radiation
a. are dangerous to the human body. b. can be tolerated by the human body. c. are beneficial to the human body. d. none of the above
Two objects are at rest on a frictionless surface. Object 1 has a mass that is twice that of Object 2. When a constant force is applied to Object 1, it accelerates through a distance d. The force is removed from Object 1 and is then applied to Object 2. At the moment when Object 2 has accelerated through the same distance d, which statements are true?
(i) p2 = 2p1 (ii) p2 = p1 (iii) p2 = ½ p1 (iv) KE2 = 2KE1 (v) KE2 = KE1 (vi) KE2 = ½ KE1
1.(i) and (iv) 2.(ii) and (vi) 3.(i) and (v) 4.(iii) and (v)Most coal deposits were formed in the
A) Cenozoic era. B) Mesozoic era. C) Paleozoic era. D) Precambrian era.