Answer the following question given this paragraph: The first period of the Paleozoic Era was the Cambrian. By the beginning of the Paleozoic, organisms evolved shells. Shells could hold their soft tissues together. Shells could protect them from predators and from drying out. Some organisms evolved external skeletons. These are called exoskeletons . Organisms with hard parts also make good fossils. Fossils from the Cambrian are much more abundant than fossils from the Precambrian. Q: The first period of the paleozoic era was called what? Choices: - carboniferous - permian - ordovician - cambrian A:
cambrian
Answer the following question given this paragraph: All chemical reactions, even exothermic reactions, need activation energy to get started. Activation energy is needed to bring reactants together so they can react. Q: What do all chemical reactions need to get started? Choices: - expression energy - kinetic energy - potential energy - activation energy A:
activation energy
Q: Answer the following question given this paragraph: Molecular and Formula Masses The molecular mass of a substance is the sum of the average masses of the atoms in one molecule of a substance. It is calculated by adding together the atomic masses of the elements in the substance, each multiplied by its subscript (written or implied) in the molecular formula. Because the units of atomic mass are atomic mass units, the units of molecular mass are also atomic mass units. The procedure for calculating molecular masses is illustrated in Example 1. Q: What is calculated by adding together the atomic masses of the elements in the substance, each multiplied by its subscript (written or implied) in the molecular formula? Choices: - mass effect - fractional mass - magnetic mass - molecular mass A:
A: molecular mass
Question: Answer the following question given this paragraph: (a) A jet airplane flying from Darwin, Australia, has an air speed of 260 m/s in a direction 5.0 south of west. It is in the jet stream, which is blowing at 35.0 m/s in a direction 15 south of east. What is the velocity of the airplane relative to the Earth? (b) Discuss whether your answers are consistent with your expectations for the effect of the wind on the plane's path. (a) In what direction would the ship in Exercise 3.57 have to travel in order to have a velocity straight north relative to the Earth, assuming its speed relative to the water remains 7.00 m/s ? (b) What would its speed be relative to the Earth? 60. (a) Another airplane is flying in a jet stream that is blowing at 45.0 m/s in a direction 20 south of east (as in Exercise 3.58). Its direction of motion relative to the Earth is 45.0 south of west, while its direction of travel relative to the air is 5.00 south of west. What is the airplane's speed relative to the air mass? (b) What is the airplane's speed relative to the Earth? 61. A sandal is dropped from the top of a 15.0-m-high mast on a ship moving at 1.75 m/s due south. Calculate the velocity of the sandal when it hits the deck of the ship: (a) relative to the ship and (b) relative to a stationary observer on shore. (c) Discuss how the answers give a consistent result for the position at which the sandal hits the deck. The velocity of the wind relative to the water is crucial to sailboats. Suppose a sailboat is in an ocean current that has a velocity of 2.20 m/s in a direction 30.0 east of north relative to the Earth. It encounters a wind that has a velocity of 4.50 m/s in a direction of 50.0 south of west relative to the Earth. What is the velocity of the wind relative to the water? 63. The great astronomer Edwin Hubble discovered that all distant galaxies are receding from our Milky Way Galaxy with velocities proportional to their distances. It appears to an observer on the Earth that we are at the center of an expanding universe. Figure 3.64 illustrates this for five galaxies... Q: The great astronomer edwin hubble discovered that all distant galaxies are receding from our milky way galaxy with velocities proportional to their what? Choices: - masses - paths - dimensions - distances A:
Answer: distances
*Question*
Answer the following question given this paragraph: In the troposphere, warm air ordinarily sits below cooler air. Q: Does warm air sit above or below cooler air in the troposphere? Choices: - above - adjacent - near - below A:
**Answer**
below
Q: Answer the following question given this paragraph: Q: What part of the plant do nutrients enter? Choices: - the seeds - the flower - the stem - the roots A:
A: the roots