instruction:
Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.
question:
In the county, the population was spread out with 23.20% under the age of 18, 7.70% from 18 to 24, 27.00% from 25 to 44, 28.00% from 45 to 64, and 14.10% who were 65 years of age or older. The median age was 40 years. For every 100 females, there were 97.00 males. For every 100 females age 18 and over, there were 96.40 males.
answer:
Which age group had the most people?

question:
Force is defined as a push or a pull acting on an object. Examples of forces include friction and gravity. Both are covered in detail later in this chapter. Another example of force is applied force. It occurs when a person or thing applies force to an object, like the girl pushing the swing in Figure 13.1. The force of the push causes the swing to move. Force is a vector because it has both size and direction. For example, the girl in Figure 13.1 is pushing the swing away from herself. Thats the direction of the force. She can give the swing a strong push or a weak push. Thats the size, or strength, of the force. Like other vectors, forces can be represented with arrows. Figure 13.2 shows some examples. The length of each arrow represents the strength of the force, and the way the arrow points represents the direction of the force. How could you use an arrow to represent the girls push on the swing in Figure 13.1? The SI unit of force is the newton (N). One newton is the amount of force that causes a mass of 1 kilogram to accelerate at 1 m/s2 . Thus, the newton can also be expressed as kgm/s2 . The newton was named for the scientist Sir Isaac Newton, who is famous for his law of gravity. Youll learn more about Sir Isaac Newton later in the chapter. More than one force may act on an object at the same time. In fact, just about all objects on Earth have at least two forces acting on them at all times. One force is gravity, which pulls objects down toward the center of Earth. The other force is an upward force that may be provided by the ground or other surface. Consider the example in Figure 13.3. A book is resting on a table. Gravity pulls the book downward with a force of 20 newtons. At the same time, the table pushes the book upward with a force of 20 newtons. The combined forces acting on the book or any other object are called the net force. This is the overall force acting on an object that takes into account all of the individual forces acting on the object. You can learn more about the concept of net force at this URL: . When two forces act on an object in opposite directions, like the book on the table, the net force is equal to the difference between the two forces. In other words, one force is subtracted from the other to calculate the net force. If the opposing forces are equal in strength, the net force is zero. Thats what happens with the book on the table. The upward force minus the downward force equals zero (20 N up - 20 N down = 0 N). Because the forces on the book are balanced, the book remains on the table and doesnt move. In addition to these downward and upward forces, which generally cancel each other out, forces may push or pull an object in other directions. Look at the dogs playing tug-of-war in Figure 13.4. One dog is pulling on the rope with a force of 10 newtons to the left. The other dog is pulling on the rope with a force of 12 newtons to the right. These opposing forces are not equal in strength, so they are unbalanced. When opposing forces are unbalanced, the net force is greater than zero. The net force on the rope is 2 newtons to the right, so the rope will move to the right. Two forces may act on an object in the same direction. You can see an example of this in Figure 13.5. After the man on the left lifts up the couch, he will push the couch to the right with a force of 25 newtons. At the same time, the man to the right is pulling the couch to the right with a force of 20 newtons. When two forces act in the same direction, the net force is equal to the sum of the forces. This always results in a stronger force than either of the individual forces
answer:
force that a person or thing exerts on to an object

question:
Water is a simple chemical compound. Each molecule of water contains two hydrogen atoms (H2 ) and one oxygen atom (O). Thats why the chemical formula for water is H2 O. If water is so simple, why is it special? Water is one of the few substances that exists on Earth in all three states of matter. Water occurs as a gas, a liquid and a solid. You drink liquid water and use it to shower. You breathe gaseous water vapor in the air. You may go ice skating on a pond covered with solid water ice in the winter. Earth is often called the water planet. Figure 13.1 shows why. If astronauts see Earth from space, this is how it looks. Notice how blue the planet appears. Thats because oceans cover much of Earths surface. Water is also found in the clouds that rise above the planet. Most of Earths water is salt water in the oceans. As Figure 13.2 shows, only 3 percent of Earths water is fresh. Freshwater is water that contains little or no dissolved salt. Most freshwater is frozen in ice caps and glaciers. Glaciers cover the peaks of some tall mountains. For example, the Cascades Mountains in North America and the Alps Mountains in Europe are capped with ice. Ice caps cover vast areas of Antarctica and Greenland. Chunks of ice frequently break off ice caps. They form icebergs that float in the oceans. Did you ever wonder where the water in your glass came from or where its been? The next time you take a drink of water, think about this. Each water molecule has probably been around for billions of years. Thats because Earths water is constantly recycled. Water is recycled through the water cycle. The water cycle is the movement of water through the oceans, atmo- sphere, land, and living things. The water cycle is powered by energy from the Sun. Figure 13.3 diagrams the water cycle. Water keeps changing state as it goes through the water cycle. This means that it can be a solid, liquid, or gas. How does water change state? How does it keep moving through the cycle? As Figure 13.3 shows, several processes are involved. Evaporation changes liquid water to water vapor. Energy from the Sun causes water to evaporate. Most evaporation is from the oceans because they cover so much area. The water vapor rises into the atmosphere. Transpiration is like evaporation because it changes liquid water to water vapor. In transpiration, plants release water vapor through their leaves. This water vapor rises into the atmosphere. Condensation changes water vapor to liquid water. As air rises higher into the atmosphere, it cools. Cool air can hold less water vapor than warm air. So some of the water vapor condenses into water droplets. Water droplets may form clouds. Precipitation is water that falls from clouds to Earths surface. Water droplets in clouds fall to Earth when they become too large to stay aloft. The water falls as rain if the air is warm. If the air is cold, the water may freeze and fall as snow, sleet, or hail. Most precipitation falls into the oceans. Some falls on land. Runoff is precipitation that flows over the surface of the land. This water may travel to a river, lake, or ocean. Runoff may pick up fertilizer and other pollutants and deliver them to the water body where it ends up. In this way, runoff may pollute bodies of water. Infiltration is the process by which water soaks into the ground. Some of the water may seep deep under- ground. Some may stay in the soil, where plants can absorb it with their roots. In all these ways, water keeps cycling. The water cycle repeats over and over again. Who knows? Maybe a water molecule that you drink today once quenched the thirst of a dinosaur.
answer:
water that falls from clouds to Earths surface