How long did the Cambrian explosion last?
A) less than 1 year
B) about a decade
C) about 10,000 years
D) about 20 million years
E) about 500 million years
D) about 20 million years
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Why is a 1-solar-mass red giant more luminous than a 1-solar-mass main-sequence star?
A) Fusion reactions are producing energy at a greater rate in the red giant. B) The red giant has a hotter core. C) The red giant's surface is hotter. D) The red giant is more massive.
You hold a 5-newton rock motionless in your hand. Regarding the forces on this rock,
A) the net force on the rock is zero. B) the downward force of gravity is balanced by the upward force of air resistance. C) there are no forces of any kind acting on the rock, because it is not moving. D) the net force on the rock is 5 newtons, directed downward. E) the net force on the rock is 5 newtons, directed upward.
A bubble having a diameter of 1.00 cm is released from the bottom of a swimming pool where the depth is 5.00 m. What will the diameter of the bubble be when it reaches the surface? The temperature of the water at the surface is 20.0°C, whereas it is 15.0°C at the bottom. (The density of water is 1.00 × 10^3 kg/m3.)
a. 1.05 cm b. 1.15 cm c. 1.45 cm d. 1.65 cm e. 1.35 cm
What is the wavelength of a monochromatic light beam, where the photon energy is 2.00 eV? (h = 6.63 × 10^-34 J×s, c = 3.00 × 10^8 m/s, 1 nm = 10-9 m, and 1 eV = 1.6 × 10^-19 J)
a. 414 nm c. 311 nm b. 1243 nm d. 622 nm