Which of the following explains why the Earth orbits the sun rather than the sun orbiting the Earth? A. Earth has much smaller mass, so the gravitational force accelerates the Earth much more than it accelerates the sun.
B. The force of Earths gravity pulling on the sun has a smaller magnitude than the force of the sun pulling on Earth.
C. While the Earth is pulled toward the sun with a gravitational force, the sun is not pulled toward the Earth be a gravitational force.
D. Even though the sun is pulled toward the Earth, the force is opposed by forces from the gravity of the planets.

The particle in a two-dimensional well is a useful model for the motion of electrons around the indole ring (3), the conjugated cycle found in the side chain of tryptophan. we may regard indole as a rectangle with sides of length 280 pm and 450 pm, with 10 electrons in the conjugated p system. as in case study 9.1, we assume that in the ground state of the molecule each quantized level is occupied by two electrons. (a) calculate the energy of an electron in the highest occupied level. (b) calculate the frequency of radiation that can induce a transition between the highest occupied and lowest unoccupied levels. 9.27 electrons around the porphine ring (4), the conjugated macrocycle that forms the structural basis of the heme group and the chlorophylls. we may treat the group as a circular ring of radius 440 pm, with 20 electrons in the conjugated system moving along the perimeter of the ring. as in exercise 9.26, assume that in the ground state of the molecule quantized each level is occupied by two electrons. (a) calculate the energy and angular momentum of an electron in the highest occupied level. (b) calculate the frequency of radiation that can induce a transition between the highest occupied and lowest unoccupied levels.

The coefficient of friction is a number that represents the resistance to sliding between two in contact with one another.

Difference between series and parallel circuits