The Reconquest: The aim of the Crusades in Spain was the eviction of the Muslims. After the recovery of Jerusalem in 1099, it took four hundred years of sieges and battles, treaties, betrayals, and yet more battles, before Christian kings and warlords succeeded in subduing the Moors. On 10 September 1229, a Catalan army led by King Jaume I of Aragon and Catalunya took the Mallorcan shore near the present-day resort of Santa Ponca. The defenders retreated inside the walls of Palma, but on the last day of 1229 the city fell, and pockets of resistance throughout the island were also defeated. Jaume I proved to be an enlightened ruler who profited from the talents of the Moorsconverted by force to Christianityas well as of the island's large Jewish and Genoese trading communities. Mallorca prospered. The Moors on Menorca speedily agreed to pay an annual tribute to Aragon and were left in peace. The island's tranquility lasted until 1287, when Alfonso III of Aragon, smarting over a series of humiliations at the hands of his nobles, found a pretext for invasion. The Moors were defeated and expelled or killed. In contrast to Mallorca, Menorca's economy was devastated for decades. Jaume I died after reigning in Aragon for six decades, but he made the cardinal error of dividing between his sons the lands he had fought for so long to unite. At first this resulted in an Independent Kingdom of Mallorca, under Jaume II, followed by Sanc and Jaume III. But family rivalry triggered the overthrow of Jaume III by his cousin Pedro IV, who then seized the Balearics for Aragon. Attempting a comeback, Jaume was killed in battle near Llucmajor in 1349. A newly unified Christian Spain under the Catholic Monarchs, Ferdinand and Isabella, completed the Reconquest, defeating the only Moorish enclave left on the Iberian peninsula, Granada, in 1492. However, the centralized kingdom failed to incorporate the Balearics politically or economically.

Question: "What kind of ruler was King Jaume 1?"

OPTIONS:
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- yes

Answer: "Enlightened"

Response: yes

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.

Question: "How many forces does an object have?"

OPTIONS:
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- yes

Answer: "One"

Response: no

On Thursday Fort Waelhem succumbed after a magnificent resistance. The garrison held it until it was a mere heap of ruins, and, indeed, they had the greatest difficulty in making their way out. I think that there is very little doubt that the Germans were using against these forts their largest guns, the great 42-centimetre howitzers. It is known that two of these were brought northwards past Brussels after the fall of Maubeuge, and a fragment which was given to us was almost conclusive. It was brought to us one morning as an offering by a grateful patient, and it came from the neighbourhood of Fort Waelhem. It was a mass of polished steel two feet long, a foot wide, and three inches thick, and it weighed about fifty pounds. It was very irregular in shape, with edges sharp as razors, without a particle of rust upon it. It had been picked up where it fell still hot, and it was by far the finest fragment of shell I have ever seen. Alas we had to leave it behind, and it lies buried in a back-garden beside our hospital. Some day it will be dug up, and will be exhibited as conclusive evidence that the Germans did use their big guns in shelling the town.

Question: "What did the gun fragment look like?"

OPTIONS:
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- yes

Answer: "It was a rust covered piece of metal, picked up as it fell"

Response: no

If you have a mass of 50 kg on Earth, what is your weight in newtons? An object with more mass is pulled by gravity with greater force. Mass and weight are closely related. However, the weight of an object can change if the force of gravity changes. On Earth, the force of gravity is the same everywhere. So how does the force of gravity change? It doesnt if you stay on Earth. What if we travel to another planet or moon in our solar system? Look at the photo of astronaut Edwin E. Aldrin Jr. taken by fellow astronaut Neil Armstrong in the Figure. They were the first humans to walk on the moon. An astronaut weighs less on the moon than he would on Earth. This is because the moons gravity is weaker than Earths. The astronauts mass, on the other hand, did not change. He still contained the same amount of matter on the moon as he did on Earth. If the astronaut weighed 175 pounds on Earth, he would have weighed only 29 pounds on the moon. If his mass on Earth was 80 kg, what would his mass have been on the moon? [Figure 3]

Question: "How does the force of gravity affect your weight?"

OPTIONS:
- no
- yes

Answer: "More the force of gravity, less the weight"

Response:
no