The main reason for the wall's construction had always been defense. Since China's first dynasty, the empire faced a near-constant threat of attack from the nomadic tribes to the north. This included those famed Mongols as well as lesser-known groups like the Xiongnu and the Göktürks.
Acceleration is non zero but the velocity is zero.
Answer: Option 2.
<u>Explanation:</u>
Acceleration is the speed that an object gains with in a short period of time. In the language of Mechanics, Acceleration is the change in the velocities of the objects with respect to the time. So when a ball is thrown up in the air, there will be some acceleration and there will be some speed that the ball will gain when thrown up.
Velocity is the speed of an object but in a particular direction. Velocity of an object is the rate of change of the position of the object with respect to the frame of reference of that frame. So the velocity of the ball up in the air is zero.
There are three main reasons why people are concerned that cell phones (also known as “mobile” or “wireless” telephones) might have the potential to cause certain types of cancer or other health problems:
Cell phones emit radiofrequency energy (radio waves), a form of non-ionizing radiation, from their antennas. Tissues nearest to the antenna can absorb this energy.
The number of cell phone users has increased rapidly. As of December 2014, there were more than 327.5 million cell phone subscribers in the United States, according to the Cellular Telecommunications and Internet Association. This is a nearly threefold increase from the 110 million users in 2000. Globally, the number of subscriptions is estimated by the International Telecommunications Union to be 5 billion.
Over time, the number of cell phone calls per day, the length of each call, and the amount of time people use cell phones have increased. However, improvements in cell phone technology have resulted in devices that have lower power outputs than earlier models.
Answer: I think it is A
Explanation: There are millions of lakes in the world. They are found on every continent and in every kind of environment—in mountains and deserts, on plains, and near seashores.
