题干

如图甲所示是探究“阻力对物体运动的影响”的实验装置,图乙所示是探究“物体的动能与质量的关系”的实验装置.关于这两个实验的说法中正确的是(  )

A:两个实验都控制物体从同一高度自由下滑,是为了保证物体到水平面时的初速度相同

B:甲实验可以推理出,如果运动的物体不受力,它将以恒定不变的速度一直运动下去

C:乙实验可得出物体的速度一定时,质量越大,动能越大

D:甲、乙实验中物体运动时,机械能的总量始终保持不变

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答案(点此获取答案解析)

A,B,C

同类题4

阅读理解

    There was once a captain who loved money so much that he cheated his sailors at the end of every voyage and took their wages (工资).

    On the last day of one voyage, the ship was in a small port. It was winter time, and the sea was very cold, so the captain said to his sailors, “If one of you stays in the water during the whole night, I will give him my ship. But if he comes out before the sun appears, I shall get his wages.”

    The sailors (船员) had heard about the captain's cheating, so they didn't trust him. But then one of them, who thought that he was cleverer than the captain, said that he would do it. He got into the water, and, though it was very cold, he stayed in it. When it was nearly morning, some fishermen lit a fire on the shore about half a mile away.

    “You are cheating,” the captain said to the sailor. “The fire's warming you.”

    “But it's half a mile away!” said the sailor.

    “A fire's fire,” answered the captain. “I have won.”

    The sailor came out of the water, and said, “Perhaps you think that you are clever because you have won my wages, but you can't cook a chicken.”

    “I can,” answered the captain.

    “If you cook this chicken,” said the sailor, “I shall work for you without wages for seven years, but if you can't, you will give me your ship.”

The captain agreed, took the chicken and said, “Where's the fire?”

    “There it is,” answered the sailor. “On the shore.”

    “But it's half a mile away,” said the captain angrily.

    “‘A fire's fire,' you said,” answered the sailor. “If it is enough to warm me in the water, it is enough to cook your chicken.”