Which of the following statements best summarizes current evidence concerning dark matter in individual galaxies and in clusters of galaxies?
A) Dark matter is the dominant form of mass in both clusters and in individual galaxies.
B) Dark matter is present between galaxies in clusters, but not within individual galaxies.
C) Dark matter is present in individual galaxies, but there is no evidence that it can exist between the galaxies in a cluster.
D) Within individual galaxies, dark matter is always concentrated near the galactic center, and within clusters it is always concentrated near the cluster center.
A) Dark matter is the dominant form of mass in both clusters and in individual galaxies.
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Nuclear reactors use nuclear _____________ to generate energy whereas the Sun uses nuclear ____________ to generate energy
Fill in the blank(s) with correct word
The planet Venus requires 225 days to orbit the Sun, which has a mass M = 1.99 × 1030 kg, in an almost circular trajectory. Calculate the radius of the orbit and the orbital speed of Venus as it circles the Sun.
What will be an ideal response?
A heat conducting rod, 1.40 m long, is made of an aluminum section that is 0.50 m long and a copper section that is 0.90 m long. Both sections have cross-sectional areas of of 0.00040 m2
The aluminum end and the copper end are maintained at temperatures of 40°C and 280°C, respectively. The thermal conductivity of aluminum is 205 W/m?K of copper is 385 W/m?K. The rate at which heat is conducted in the rod is closest to A) 20 W. B) 18 W. C) 23 W. D) 25 W. E) 28 W.
A block is projected with speed v across a horizontal surface and slides to a stop due to friction. The same block is then projected with the same speed v up an incline where is slides to a stop due to friction. In which case did the total mechanical energy of the block decrease the least?
a. This problem cannot be solved since it was not indicated whether the horizontal surface and the incline both had the same coefficient of kinetic friction. b. The case on the horizontal surface had the least decrease in total mechanical energy. c. The case on the inclined surface had the least decrease in total mechanical energy. d. In both cases the decrease in mechanical energy was the same.