Answers by visitors named: Rick_the_chemist

The angles are simple because you have an equilateral triangle. In any triangle, the sum of the internal angles must be 180 degrees. An equilateral triangle is also equiangular. Therefore, the angles are simply 60 degrees each (3 * 60 degrees/angle = 180 degrees) The two charges will repel each other (as drwls said) along a line that bisects the 60 degree angles. Remember that there are *two* charges repelling each single charge. I think that's why you're getting 3.1 N instead of 6.2N. Multiply by 2.

The density of water is 1 g/cm^3. Archimedes' principle says that the "buoyancy" (the upward force) is equal to the weight of water that is displaced. You're only given the density. Therefore, you can assume whatever mass of ice that you wish. If you pick 1 gram of ice, the volume of ice will be 1 gram / (0.92 g/cm^3) = 1.087 cm^3 If you immerse this in water, it will displace 1 gram of water. Since the density of water is 1 gram/cc, it will displace 1 cm^3 of water. You have 1 cm^3 of water being displaced, and a total ice volume of 1.087 cm^3. Therefore, 0.087 cm^3 of ice is above the water 0.087 cm^3 / 1.087 cm^3 x 100% = 8%

X = the cost of MaineCellular's plan P = the cost of Portland Wireless' plan T = time in minutes. X = $12 + $0.10 T P = $20 + $0.05 T P = X at the number of minutes that the two costs cross. So, set X = P $12 + $0.10 T = $20 + $0.05 T Solve for T. Once you have T, anything less than T minutes will give one of the plans an edge. Which one? Anything greater than T minutes will give the other plan the edge.