Input: What if two children push a swing at the same time? Would the swing go higher? Yes, together their force would be more. It is common for forces to be combined. Most objects on Earth have at least two forces acting on them. Do you know what one of them is? Of course, that force is gravity. How many forces do you have on you right now? Gravity pulls you down toward the center of Earth. Your legs exert a downward force. They hold you up against the pull of gravity. Consider the example in Figure 1.3. A book is resting on a table. Gravity pulls the book downward. It has a force of 20 newtons. At the same time, the table pushes the book upward. Its force is also 20 newtons. The table opposes the pull of gravity.
"Do all objects on Earth have force?" is "Yes"?
Output: yes
Input: For thousands of years, people have found fossils. The fossils caused curiosity about Earths past. How did these organisms live? What type of world did they live in? Fossils can tell us a lot about Earths history. In ancient times, fossils inspired myths and stories. These stories included tales of monsters and other incredible creatures. What type of creature do you know that could inspire such stories? Of course, dinosaur fossils were once mistaken for dragons bones. Two thousand years ago, people discovered fossils in China. At the time, they were thought to be dragon bones. We know now that these were not bones, but fossils. So what is the difference?
"What did these stories consist of?" is "humans"?
Output: no
Input: Living things need non-living matter as well as energy. What do you think matter is used for? One thing is to build bodies. They also need it to carry out the processes of life. Any non-living matter that living things need is called a nutrient. Carbon and nitrogen are examples of nutrients. Unlike energy, matter is recycled in ecosystems. You can see how in Figure 3.11. Decomposers release nutrients when they break down dead organisms. The nutrients are taken up by plants through their roots. The nutrients pass to primary consumers when they eat the plants. The nutrients pass to higher level consumers when they eat lower level consumers. When living things die, the cycle repeats.
"What are two things matter is used for?" is "Eating plants"?
Output:
no