Input: Magnets are able to place a force on certain materials. This force is called a magnetic force. The force a magnet exerts is a little different from the forces you may normally think about. You exert a force on a book when you lift it. You also exert a force on the pedals of your bicycle. In both those cases, those forces cause a change. The change you see in both these cases is called motion. Magnets, too, can produce change. They can produce motion just like you do. Unlike you, magnets do not have to touch something to exert a force. A magnetic force is exerted over a distance. Thats right, a magnet can push or pull certain items without ever touching them. Thats how the maglev train works. Do you know another type of force that does not require objects to touch? These forces are known as non-contact forces. Another type of non-contact force you may be familiar with is gravity. Gravity too can cause changes in motion. Gravity holds our moon in orbit without touching it.

Does the response "Forces exerted without touching anything" correctly answer the question "What are non contact forces?"?

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Output: yes

Input: Reducing resource use means just what it says using fewer resources. There are lots of ways to reduce our use of resources. Buy durable goods. Choose items that are well made so they will last longer. Youll buy fewer items in the long run, so youll save money as well as resources. Thats a win-win! Repair rather than replace. Fix your bike rather than buying a new one. Sew on a button instead of buying a new shirt. Youll use fewer resources and save money. Buy only what you need. Dont buy a gallon of milk if you can only drink half of it before it spoils. Instead, buy a half gallon and drink all of it. You wont be wasting resources (or money!) Buy local. For example, buy local produce at a farmers market, like the one in Figure 2.20. A lot of resources are saved by not shipping goods long distances. Products bought at farmers markets use less packaging, too! About a third of what we throw out is packaging.

Does the response "Less packaging is used" correctly answer the question "How can you reduce the use of resources by buying local?"?

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Output: yes

Input: "What goes up must come down." You have probably heard that statement before. At one time this statement was true, but no longer. Since the 1960s, we have sent many spacecraft into space. Some are still traveling away from Earth. So it is possible to overcome gravity. Do you need a giant rocket to overcome gravity? No, you actually overcome gravity every day. Think about when you climb a set of stairs. When you do, you are overcoming gravity. What if you jump on a trampoline? You are overcoming gravity for a few seconds. Everyone can overcome gravity. You just need to apply a force larger than gravity. Think about that the next time you jump into the air. You are overcoming gravity for a brief second. Enjoy it while it lasts. Eventually, gravity will win the battle.

Does the response "True" correctly answer the question "Are you overcoming gravity when you climb a set of stairs?"?

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Output: yes

Input: Static electricity is like a teeter-totter. What happens if a teeter-totter is balanced? Correct! It does not move. What about when its not balanced? Yes, it will now begin to move. Charges move when they are not balanced. Charges can build up by friction. Maybe you rub your feet on a wool mat or carpet. Rubber soled shoes readily gain charges. The wool carpet easily gives up charges. The two items become unbalanced. One item has a positive charge. The other has a negative charge. The difference in charge is called static electricity. Just like the teeter-totter, something is going to move. Positive charges build up on the mat. Negative charges build up on you.

Does the response "It does not move" correctly answer the question "What happens if static electricity is not balanced?"?

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- yes
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Output:
no