Tutor profile: Sarah P.
A certain distance runner can run at a rate of 7 mph for up to 1 hour, then must slow to a rate of 6 mph for an additional hour. A sprinter can run at a rate of 10 mph for up to 20 minutes, but them must rest for 20 minutes before running again, at a rate that decreases by 10% after each rest. If the two enter a race, who will be further along after 90 minutes? how many miles further will he be?
The distance runner will have run 10 miles after 90 minutes, 7 miles in the first hour, and 3 miles in the last 30 minutes (since he was running at 6 mph during that time, and 6/2 is 3). The sprinter will run 10 miles in the first 20 minutes, 0 in the second 20 minutes )minutes 20-40), 9 miles in the third 20 minutes (minutes 40-60), 0 in the fourth 20 minutes (minutes 60-80), and 4.05 miles in the last 10 minutes (running at a rate of (-(9 x .1) = 8.1 mph). The sprinter will have run 23.05 miles in the 90 minutes. Therefore, he will be 13.05 miles ahead of the distance runner.
Describe and compare the different types of chemical bonds.
Types of matter need chemical bonds in order to make more complex substances. Atoms can "stick" together through chemical bonds when a positive and negative force attract each other. All atoms are most stable when they have a certain number of electrons, so atoms gain, lose, or share electrons, causing charges to form. All atoms can be loosely associated with each other through a type of bond called Vanderwaal forces. The electrons in different atoms can momentarily aggregate to one side of the atom, causing a temporary pole, either positive or negative, depending on the location of the electrons. These polarized atoms can them attract other atoms. This is the weakest force. Another type of bond occurs when atoms share electrons, these are called covalent bonds. Covalent bonds can either be polar (one atom "hogs" the electrons) or non-polar (the electrons are shared equally). Hydrogen bonds are a polar covalent bond. Metallic bonds also result from the sharing of electrons, among conductive metal ions Covalent bonds are of a medium strength. The strongest type of chemical bond is ionic bonds, resulting when one atom loses or gains electrons, causing it to be charged either positively or negatively, which attracts another atom of opposite charge.
Describe how the structure of DNA relates to its function as the genetic material for all life.
DNA's structure makes it one of the most suitable forms for conveying the genetic information of all the diverse life forms on Earth. Because DNA is in long strands, consisting of nitrogenous bases, it has the unique capability of acting as a "code". Although there are only 4 nitrogenous bases, their sequence (in groups of 3) allows for translation into making proteins that are vital for all life functions. The endless combinations of nitrogenous base codes means that their can be a nearly infinite number of possible proteins, accounting for the diversity of life. Because the two purine bases and two pyrimidine bases pair together, DNA is in a double helix form, allowing for DNA's easy replication and transmission to offspring.
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