Answer the following question given this paragraph: Some machines change the direction of the force applied by the user. They may or may not also change the strength of the force or the distance over which the force is applied. Two examples of machines that work this way are the claw ends of hammers and flagpole pulleys. You can see in the Figure below how each of these machines works. In both cases, the direction of the force applied by the user is reversed by the machine. Q: Claw ends of hammers and flagpole pulleys are examples of simple machines that reverse what? Choices: - direction of power - direction of work - direction of friction - direction of force A:
direction of force
Answer the following question given this paragraph: Good conductors have large numbers of free charges in them. In metals, the free charges are free electrons. Figure 20.6 shows how free electrons move through an ordinary conductor. The distance that an individual electron can move between collisions with atoms or other electrons is quite small. The electron paths thus appear nearly random, like the motion of atoms in a gas. But there is an electric field in the conductor that causes the electrons to drift in the direction shown (opposite to the field, since they are negative). The drift velocity v d is the average velocity of the free charges. Drift velocity is quite small, since there are so many free charges. If we have an estimate of the density of free electrons in a conductor, we can calculate the drift velocity for a given current. The larger the density, the lower the velocity required for a given current. Q: Why is the drift velocity negligible? Choices: - shows free charges - less free charges - need free charges - many free charges A:
many free charges
Q: Answer the following question given this paragraph: Upwelling brings nutrients to the surface from the ocean floor. Nutrients are important resources for ocean life. However, they aren't the only resources on the ocean floor. Q: What process brings nutrients from the ocean's floor to its surface? Choices: - Down welling - coastal swell - Tides - upwelling A:
A: upwelling
Question: Answer the following question given this paragraph: A natural resource is anything in nature that humans need. Metals and fossil fuels are natural resources. But so are water, sunlight, soil, and wind. Even living things are natural resources. Q: Metals, fossil fuels, and water are all examples of what type of resource? Choices: - ores - recyclables - renewable resources - natural resources A:
Answer: natural resources
*Question*
Answer the following question given this paragraph: Fishes Modern fishes include an estimated 31,000 species. Fishes were the earliest vertebrates, and jawless fishes were the earliest of these. Jawless fishesthe present day hagfishes and lampreyshave a distinct cranium and complex sense organs including eyes, distinguishing them from the invertebrate chordates. The jawed fishes evolved later and are extraordinarily diverse today. Fishes are active feeders, rather than sessile, suspension feeders. Jawless Fishes Jawless fishes are craniates (which includes all the chordate groups except the tunicates and lancelets) that represent an ancient vertebrate lineage that arose over one half-billion years ago. Some of the earliest jawless fishes were the ostracoderms (which translates as "shell-skin"). Ostracoderms, now extinct, were vertebrate fishes encased in bony armor, unlike present-day jawless fishes, which lack bone in their scales. The clade Myxini includes 67 species of hagfishes. Hagfishes are eel-like scavengers that live on the ocean floor and feed on dead invertebrates, other fishes, and marine mammals (Figure 15.37a). Hagfishes are entirely marine and are found in oceans around the world except for the polar regions. A unique feature of these animals is the slime glands beneath the skin that are able to release an extraordinary amount of mucus through surface pores. This mucus may allow the hagfish to escape from the grip of predators. Hagfish are known to enter the bodies of dead or dying organisms to devour them from the inside. Q: Fishes were the earliest example of what subphylum, and jawless fishes were the earliest of these? Choices: - grasses - ferns - mammals - vertebrates A:
**Answer**
vertebrates
*Question*
Answer the following question given this paragraph: So how is the blood kept from flowing back on itself? Valves ( Figure below ) in the heart keep the blood flowing in one direction. The valves do this by opening and closing in one direction only. Blood only moves forward through the heart. The valves stop the blood from flowing backward. There are four valves of the heart. Q: How many valves are in the heart? Choices: - one - six - two - four A:
**Answer**
four