Radioactivity Basics: When an unstable nucleus decays by emitting an alpha particle, the atomic mass number A of the nucleus
A. increases by 4.
B. increases by 2.
C. decreases by 2.
D. decreases by 4.
E. remains unchanged.
Answer: D
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How do we most accurately measure the distance to the Moon?
A. We measure the lunar period and use Kepler's Third Law. B. We measure its angular size and compare it to its actual diameter, which gives us its distance. C. We bounce a pulse of light off the lunar surface and measure how long the trip takes. D. We know how long it took Apollo astronauts to get there, and how fast the rocket traveled. E. All of these choices provide equally accurate measurements.
A simply supported beam with proportional loading (P 5 4.1 kN) has span length L 5 5 m. Load P is 1.2 m from support A and load 2P is 1.5 m from support B. The bending moment just left of load 2P is approx-imately:
(A) 5.7 kN?m
(B) 6.2 kN?m
(C) 9.1 kN?m
(D) 10.1 kN?m
A body oscillates with simple harmonic motion along the x axis. Its displacement varies with time according to the equation x = 5 sin (?t + ?/3). The phase (in rad) of the motion at t = 2 s is
A. 7?/3. B. ?/3. C. ?. D. 5?/3. E. 2?.
What distinguishes work done by conservative versus nonconservative forces?
What will be an ideal response?