What holds galaxy clusters together?
A. the strong force
B. the cosmological constant force
C. the electromagnetic force
D. gravity
E. the pressure from the cosmic background radiation
Answer: D
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Radioactive Decay: The decay constant of a radioactive nuclide is 3.1 × 10-3 s-1. At a given instant, the activity of a specimen of the nuclide is 70 kBq. How much later has the activity declined to 10 kBq?
A. 630 s B. 690 s C. 750 s D. 820 s E. 880 s
A road bicycle racer rides down the highway from Pike’s peak. During one stretch of the ride, he descends 150 m while accelerating from 35 km/hr to some final speed. Assuming rolling friction and air resistance to be negligible, what is that final speed?
A. 113 km/h B. 118 km/h C. 148 km/h D. 169 km/h
A hunter aims a rifle at an angle of 10° above the horizontal. The hunter fires a bullet while simultaneously dropping another bullet from the side of the rifle. The bullet to hit the ground first is
A) the dropped one. B) the fired one. C) both hit at the same time
Monochromatic light (? = 500 nm) is incident on a soap bubble (n = 1.40). What is the wavelength of the light (in nm) in the bubble film?
a. 255 b. 500 c. 700 d. 357 e. 422