Which of the following best describes convection?
A) It is the process by which rocks sink in water.
B) It is the process in which warm material expands and rises while cool material contracts and falls.
C) It is the process in which warm material gets even warmer and cool material gets even cooler.
D) It is the process in which a liquid separates according to density, such as oil and water separating in a jar.
E) It is the process in which bubbles of gas move upward through a liquid of the same temperature.
B
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An eyeglass lens is cut with one surface having a radius R1 and the other surface having a radius R2, with R1 < R2 . Both positive radii are measured from the same side with R2 being the side closer to the eye. Is this convex-concave lens a converging lens or a diverging lens?
a. This is neither, since a lens cannot be made this way. b. This is a diverging lens. c. This can be either a converging or diverging lens, as more information is needed for a final determination. d. This is a converging lens.
Angular Momentum: Three solid, uniform, cylindrical flywheels, each of mass 65.0 kg and radius 1.47 m, rotate independently around a common axis through their centers. Two of the flywheels rotate in one direction at 8.94 rad/s, but the other one rotates in the opposite direction at 3.42 rad/s. Calculate the magnitude of the net angular momentum of the system.
A. 1020 kg ? m2/s B. 1500 kg ? m2/s C. 975 kg ? m2/s D. 940 kg ? m2/s
A 3.50 kg block is pulled along a moving conveyor belt at a constant speed of 0.500 m/s relative to a stationary observer while the belt moves at a constant speed of 0.200 m/s in the same direction. If the coefficient of kinetic friction is 0.400, the magnitude of the mechanical energy dissipated, in J, caused by the force of friction on the block in 8.00 s is
a. 5.6. b. 22.0. c. 32.9. d. 54.8. e. 76.8.
Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram?
A) mass on the horizontal axis and luminosity on the vertical axis B) surface temperature on the horizontal axis and luminosity on the vertical axis C) mass on the horizontal axis and stellar age on the vertical axis D) interior temperature on the horizontal axis and mass on the vertical axis E) surface temperature on the horizontal axis and radius on the vertical axis