(CNN) -- Jo-Wilfried Tsonga ended Roger Federer's hopes of winning a record-equaling seventh Wimbledon title on Wednesday as the French 12th seed staged a stunning fightback to reach the semifinals. Federer appeared to be cruising into the last four after winning the first two sets, but Tsonga inflicted the Swiss world No. 3's first defeat from that vantage point in 179 grand slam matches. It was only the third time in the 29-year-old's glittering career that the 16-time grand slam champion had surrendered a two-set lead. Tsonga, ranked 19th in the world, triumphed 3-6 6-7 (3-7) 6-4 6-4 6-4 on Centre Court, serving out to love as he earned a clash with second seed Novak Djokovic. The Serbian, who beat Tsonga in the 2008 Australian Open final, ended the dream run of Australian 18-year-old Bernard Tomic. Tsonga defeated Federer for just the second time in six meetings, their first on grass. "It was amazing. I played unbelievable. It's never easy to come back against Roger. I'm so happy, it's crazy," the 26-year-old told reporters after reaching the semifinals at Wimbledon for the first time. "He's the biggest champion in the sport. He has achieved so much and is the best player in the world. To be two sets down and come back was unbelievable. I served really well. Against Djokovic I will have to come out and do the same again." Federer has now lost in the quarterfinals two years in a row, being beaten by eventual runner-up Tomas Berdych in 2010. "Jo played great. Really from start to finish I don't remember seeing a break point after I broke him in the first game," Federer said.

Question: "Who came back against Federer?"

Answer: "Novak Djokovic"

Response: no

Gravitational Potential Energy is affected by position. Like the leaves on trees, anything that is raised up has the potential to fall. It has potential energy. You can see examples of people with gravitational potential energy in 1.5 Figure below. Gravitational potential energy depends on two things. It depends on its weight, because a large falling rock can do more damage than a leaf falling from a tree. It also depends on its height above the ground. Like the skateboarder, the higher the ramp, the faster he will be going when he reaches the bottom. Like all energy, gravitational potential energy has the ability to do work. In this case, weight has the potential to deliver a force. More important for us is that it has the ability to cause change. What kind of change you may ask? Gravitational potential energy has the ability to cause motion.

Question: "What are the two things gravitational energy depends on?"

Answer: "Weight of the object and its height above the ground"

Response: yes

Expansion quickly peaked however, and the European powers who had carved up the New World set about testing each other in dynastic conflicts and colonial rivalry. The English were the main rivals of the Dutch on the high seas, and there were several wars between the two in the 17th and 18th centuries. In 16651667 the Dutch sailed up the River Medway and sank the British fleet moored there. The 18th century saw Amsterdam grow into the foremost financial center in the world, but the seeds of decline had already been planted. When the English colonies in New England rose up in revolt against the British, they found ready Ailies in the Dutch. From their colonies in the Caribbean they sent caches of arms and ammunition. The British were furious and went to war in 1780, destroying the Dutch navy and signaling a sudden decline in power and influence from which the Netherlands never recovered. Trade suffered to such an extent that in 1791 the VOC went into liquidation. In the latter part of the century there were anti-Orange demonstrations by pro-French factions in the country, and in 1795 Napoleon Bonaparte took the Netherlands in his epic march across Europe. Under the yoke of another foreign power, and with trade at an all time low, the Golden Age was truly dead. The Return of the House of Orange Napoleon installed his brother Louis as King of Holland and he chose to take the fine Town Hall on Dam Square as his palacenow the Koninklijk Palace. But only four years later he fled the city after civil disturbances broke out when he raised taxes. When Napoleon's bubble burst and French power began to wane, William of Orange emerged from exile and was proclaimed king in 1813. Amsterdam had to work its way out of economic decline, but throughout the 19th century the city grew steadily. Industrialization changed the city. With the building of the Central Station at the end of the century, Amsterdam turned its back on its seafaring past and looked towards the mechanical age for its future. The station was built over the old harbor wall and some of the oldest canals in the city center were filled in to allow better access to motorized vehicles. Dam Square was landlocked for the first time in its history.

Question: "Which countries did the Netherlands have problems with?"

Answer: "England and France"

Response: yes

Earth processes have not changed over time. The way things happen now is the same way things happened in the past. Mountains grow and mountains slowly wear away. The same process is at work the same as it was billions of years ago. As the environment changes, living creatures adapt. They change over time. Some organisms may not be able to adapt. They become extinct. Becoming extinct means they die out completely. Some geologists study the history of the Earth. They want to learn about Earths past. They use clues from rocks and fossils. They use these clues to make sense of events. The goal is to place things in the order they happened. They also want to know how long it took for those events to happen.

Question: "According to this passage, on what planet do mountains grow and wear away?"

Answer: "The Earth"

Response:
yes