user: Problem: I read this background article the other day: The mechanical advantage of a machine is the factor by which it changes the force applied to the machine. Many machines increase the force applied to them, and this is how they make work easier. Compound machines tend to have a greater mechanical advantage than simple machines. That’s because the mechanical advantage of a compound machine equals the product of the mechanical advantages of all its component simple machines. The greater the number of simple machines it contains, the greater its mechanical advantage tends to be.  I am facing a new situation today: David was studying the processes involved in a machine. He collected a simple machine. He tagged it as case A. To compare it with compound machines, he collected two compound machines, case B and case C. Case B is a compound machine with few simple machines. And, case C is a compound machine with many simple machines.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which machine would have smaller mechanical advantage, case B or case C?

A: case B


Problem: I read this background article the other day: Geologists study earthquake waves to “see” Earth's interior. Waves of energy radiate out from an earthquake’s focus. These waves are called seismic waves ( Figure below ). Seismic waves go different speeds through different materials. They change speed when they go from one type of material to another. This causes them to bend. Some seismic waves do not travel through liquids or gases. They just stop. Scientists use information from seismic waves to understand what makes up the Earth’s interior.  I am facing a new situation today: Two friends met after 20 years and had a beer together. Vlad was a geologist and studied earthquakes. Mort was a pedologist and studied soils. They had some interesting conversations that night.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which friend studied less about seismic waves bending?

A: Mort


Problem: I read this background article the other day: Hepatitis viruses can develop into a chronic viral infection that leads to liver cancer. Infection by human T-lymphotropic virus can lead to tropical spastic paraparesis and adult T-cell leukaemia. Human papillomaviruses are an established cause of cancers of cervix, skin, anus, and penis. Within the Herpesviridae, Kaposi's sarcoma-associated herpesvirus causes Kaposi's sarcoma and body-cavity lymphoma, and Epstein–Barr virus causes Burkitt's lymphoma, Hodgkin's lymphoma, B lymphoproliferative disorder, and nasopharyngeal carcinoma. Merkel cell polyomavirus closely related to SV40 and mouse polyomaviruses that have been used as animal models for cancer viruses for over 50 years.  I am facing a new situation today: Two medical students had to study about viruses that cause cancers in humans. Brady studied about hepatitis viruses, while Dean studied about human papillomaviruses and Herpesviridae.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which student read less about cancers of the anus?

A: Brady


Problem: I read this background article the other day: Farsightedness, or hyperopia, is the condition in which distant objects are seen clearly, but nearby objects appear blurry. It occurs when the eyeball is shorter than normal (see Figure below ). This causes images to be focused in a spot that would fall behind the retina (if light could pass through the retina). Hyperopia can be corrected with convex lenses. The lenses focus images farther forward in the eye, so they fall on the retina instead of behind it.  I am facing a new situation today: Two people went to the eye doctor's office for an annual exam; James had farsightedness, while Bob had myopia.  Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which person didn't have to wear convex lenses?

A:

assistant: Bob