Which of the following stars has a spectrum that peaks at the shortest wavelength?
A) a blue star B) a red star C) a yellow star
A
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Magnifying Glass With the Image at Infinity: A person having a near point of 25 cm uses a magnifying glass with a focal length of 10 cm. What is the angular magnification of the glass for that person when her eyes are focused at infinity?
A. 1.5 B. 2.5 C. 3.5 D. 4.5
Estimate the rate of evaporation of acetone into 75ºF air from an open 4-inch-diameter by 8-inch-tall jar when the liquid acetone is 2 inches deep at the bottom of the jar and fresh air passes over the top of the jar.
What will be an ideal response?
Equilibrium: A uniform rod weighs 40 N and is 1.0 m long. It is hinged to a wall at the left end, and held in a horizontal position at the right end by a vertical string of negligible weight, as shown in the figure. What is the magnitude of the torque due to the string about a horizontal axis that passes through the hinge and is perpendicular to the rod? The hinge is very small with negligible friction.
A. 40 N ? m B. 10 N ? m C. 5.0 N ? m D. 20 N ? m E. 30 N ? m
Which of the following statements about parallax is not true?
A) The existence of stellar parallax is direct proof that Earth orbits the Sun. B) You can demonstrate parallax simply by holding up a finger and looking at it alternately from your left and right eyes. C) Ancient astronomers were unable to measure parallax and used the absence of observed parallax as an argument in favor of an Earth-centered universe. D) Measurement of stellar parallax allows us to determine distances to nearby stars. E) The technique of stellar parallax was used by Hubble to determine that the Andromeda Galaxy (M 31 ) is about 2 million light-years away.