What is the difference between a population I star and a population II star?
What will be an ideal response?
Population I stars are metal rich, containing 1 to 3 percent metals, whereas Population II stars are metal poor, typically containing less than 0.1 percent metals. Population I stars are relatively young, and Population II stars are old. Population I stars belong to the disk component of the galaxy and are sometimes called disk population stars. They have nearly circular orbits in the plane of the galaxy and formed within the last few billion years. The Sun is a Population I star, as are the type I Cepheid variables. Population II stars belong to the spherical component of the galaxy and are sometimes called the halo population stars. These stars have randomly tipped orbits ranging from circular to highly elliptical. They are old stars that formed when the galaxy was young.
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A circular coil lies flat on a horizontal surface. A bar magnet is held fixed above the center of the coil with its north pole pointing downward. What is the direction of the induced current in the coil, as viewed from above?
A) clockwise B) counterclockwise C) There is no current in the coil.
A relationship such as 1 in. = 2.54 cm is a(n)
a. equivalence statement. b. base unit. c. derived unit. d. fundamental quantity.
Planet Zero has a mass of 5.0 × 1023 kg and a radius of 2.0 × 106 m. A space probe is launched vertically from the surface of Zero with an initial speed of 4.0 km/s. What is the speed of the probe when it is 3.0 × 106 m from Zero's center?
A. 3.0 km/s B. 2.2 km/s C. 1.6 km/s D. 3.7 km/s E. 5.9 km/s
A 200-N block, on a 30° incline, is being held motionless by friction. The coefficient of static friction between the block and the plane is 0.60 . The force due to friction is:
a. 104 N. c. 60 N. b. 100 N. d. 0 N.