science subset 1

A spinning cloud of interstellar dust and gas shrank under the force of gravity, producing a central star and revolving planetesimals.

Astronomers theorize that the solar system formed from a cloud of gas and dust that contracted under its own gravity and began to spin. Most of the cloud gravitated toward the center of this spinning disk, forming the sun. Smaller amounts of matter spun in the separate eddies, creating nuclei around which evolving planetesimals formed.

The Hertzsprung-Russell diagram plots the luminosity of stars as a function of their surface temperature. The luminosity increases upward on the vertical axis, while the temperature decreases left to right on the horizontal axis. The increased steepness of the graphed line above 10,000 Kelvin indicates that the change in luminosity per unit temperature increases at that point.

• C. Horizontal stresses associated with convergent plate boundaries.
• Regional metamorphism occurs during the mountain building and large-scale deformation associated with plate convergences. Large areas of metamorphic rock are formed during these episodes as compared to more limited zones created during contact metamorphism. When two plates collide, the horizontal force creates the pressures and temperatures needed to fold and melt existing rock into metamorphic rock.

• The decay rate of naturally occurring radioactive elements into other elements is predictable.
• Decay rates for many radioactive isotopes have been precisely measured and do not change under normal conditions on or near Earth's surface. A radioactive element in organic or inorganic material has decayed at the same rate since the material's formation. The date of the material can thus be calculated from the proportion of the original isotope to its stable end product currently found in the material.

• The small waves during the summer deposited sand on the beach, while the storm waves of winter cut back the beach.
• In general, the stronger the wave action on a beach, the steeper the beach profile. From April through September 2000, the relatively small waves permitted the deposition of sand, which as the summer went on extended the beach further into the ocean. By March 201, the large waves of winter storms had eroded the sand that had been deposited the previous summer, leaving a steep cross sectional profile.

• The water table will be lowered, and water from streams, lakes, and wetlands will move downward into the aquifer in response to the decrease in groundwater elevation.
• Unconfined sand-and-gravel aquifers are very permeable, permitting easy movement of water from the surface into the aquifer. When the amount of groundwater drawn from such an aquifer exceeds its recharge rate, the water table surrounding the well will drop to form a conical depression with the lowest point being at the well's uptake. Since streams, lakes, and wetlands overlying an unconfined aquifer are surface expressions of the elevation of the aquifer, the elevation of the water in these water bodies will also drop as they drain downward in response to the drop in elevation of the water table.

• Fossil fuels form over millions of years from the buried remains of organic matter deposited in low-oxygen aqueous environments.
• Fossil fuels take millions of years to form from organic material deposited in low-oxygen aquatic environments, such as swamps and certain marine settings. The lack of oxygen inhibits decomposition by microorganisms, and sediments cover the remains and partially preserve them. As the organic material is buried deeper, the increasing pressure causes chemical reactions to take place, transforming the material into carbon-rich coal, natural gas, and oil.

• The extraction of aluminum from ore uses a significantly greater amount of energy than recycling.
• It is extremely energy-intensive to extract and purify raw ore. Although recycling also requires energy and wastes some material, it is nonetheless a more energy, and cost-efficient process. These factors have increased efforts to promote recycling.

• Understanding the wave nature of light.
• Thomas Young's experiment provided evidence of the wave-like nature of light. When a beam of light of a single color was directed through two slits, Young observed alternating light and dark bands where the light passing through the two slits recombined. Young interpreted these findings as an interference pattern characteristic of waves, in which two colliding wave crests enhance each other, while a crest and trough cancel each other out.

• real and inverted
• Since the arrow is further from the lens that the focal point (0.01 m), the image formed is both inverted and real, i.e., able to be projected onto a surface. As shown in the diagram below, three reference light rays passing through the arrow’s point converge on the opposite side of the
• lens to determine the image’s size and orientation.

• Ray A goes parallel to the axis from the arrow point to the lens and
• then is refracted through focal point F. Ray B passes in a straight line
• directly through the center of the lens. Ray C passes from the arrow
• point through focal point F and then is refracted so it exits the lens
• parallel to the axis. The place where these rays converge indicates
• where the point of the projected arrow image will appear.

• Allow the equation to be used even when an object has a nonzero initial velocity.
• In the equation v = a�t, v = velocity, a = acceleration, and �t = the change in time. This equation assumes that the starting velocity equals 0 and can only be used to determine the velocity of an object initially at rest. If the object is already moving, then its velocity can be taken into account by adding v0, where v0 = the starting velocity taken at any point during the motion.

125 cm3

The depth to which an object will be submerged is based on how much water the object’s weight can displace. If the object’s density is only 25% that of water, then it can only displace 25% of an equal volume of water. When the rectangular solid floats in the water, the upward buoyant force exerted by the water equals the downward force of the solid’s weight. This balancing of forces occurs when 25% of the solid’s volume, or 125 cm3, is submerged.

• 400 N
• Pascal's law states that pressure applied to an enclosed fluid is transmitted equally throughout the liquid and container walls. Therefore when 100 N of force is applied to piston X, the pressure of the enclosed water increases throughout the container and exerts a force on piston Y equal to the ratio of the areas of the two pistons. Since the area of piston Y is four times that of piston X, the upward force of piston Y is four times 100 N, or 400 N.
• 14 In the early twentieth century, Robert Millikan created electrically charged oil droplets and then determined their electrical charge by calculating the magnitude of the electrical charge that would suspend them in midair in opposition to gravity. He found that the electrical charge on each oil droplet was always an integer multiple of what we now know as the basic unit charge. Millikan's experiment is credited with discovering:
• A. The charge on a single electron.
• Each electron carries an electrical charge approximately equal to -1.60 x 10-19. Robert Millikan discovered this experimentally by showing that the oil droplets had an electrical charge equal to some whole-number multiple of this number. After measuring the charge of thousands of oil droplets, he calculated the charge for a single electron by noting the smallest possible difference in charge found between the oil droplets.

• The charge on a single electron.Each electron
• carries an electrical charge approximately equal to -1.60 x 10-19.

• Robert Millikan discovered this experimentally by showing that the oil droplets had an electrical charge equal to some whole-number multiple of
• this number. After measuring the charge of thousands of oil droplets, he calculated the charge for a single electron by noting the smallest possible difference in charge found between the oildroplets.

• decreasing voltage
• This device is a step-down transformer used to decrease voltage. Each output-side winding receives the same voltage, induced magnetically from the alternating current in the input windings. The voltages of the output windings simply add together: more windings give a proportionate increase in voltage, fewer windings give a proportionate decrease. Thus, if more input than output windings are present, the voltage will drop.