阅读理解。
Most sharks are dangerous. The largest kind of sharks-the whale shark-has small teeth and is quite harmless
to people. However, blue sharks, tiger sharks, white sharks and hammerheads are enemies of man. Man-eaters
are always a danger to swimmers in shark waters. Sometimes, though, men have used strange methods when
they're suddenly faced with a shark.
During world War Ⅱ, soldiers and sailors whose boats or planes were destroyed drifted (漂流) helplessly
on the ocean in small rafts (筏子). While waiting to be saved, the men had to struggle to stay alive and were
often attacked by sharks. In some cases, they had few weapons to protect themselves with. They found that
just splashing (溅水) water seemed to help keep the sharks away.
One sailor was swimming for his life in the Atlantic Ocean after his boat had been blown up. He saw a
shark swimming towards him. He hit the shark with his bare fist, and that drove it off.
Once, in Australia, a fisherman was fishing after sunset. He hooked a big fish and drew it towards the shore. His line broke when the fish was only a few yards from the shore. The fisherman waded (涉水) into the water
to try to catch it with his hands. In the dim light, it looked like the kind of fish that could be dealt with without
danger.
He put his arms around the fish and wrestled with it. Dragging it to the beach turned out to be harder than
he had expected, but at last he pulled it in. When he turned a light on it, he was amazed. He had caught a shark.
It was small for a shark, but it was the man-eating type and was about as long as a tall man. In a word, the
best way to deal with sharks is to keep far away from them.
1. The shark that is least dangerous to man is the _______.
A. white shark
B. whale shark
C. tiger shark
D. hammerhead shark
2. This story tells you that sharks are usually ________.
A. friendly
B. small
C. afraid of people
D. dangerous
3. After the Australian fisherman found he had caught a shark, he was ________.
A. surprised
B. frightened
C. unhappy
D. angry
4. This story tells you that the best way to handle sharks is to ________.
A. hit them with your fist
B. keep far away from them
C. splash water
D. wrestle with them
5. The passage mainly tells us something ________.
A. about fishing sharks
B. about sharks
C. how to eat sharks
D. that sharks are man's enemies
（2）
（3）12.5J
解得 
………………………………（2分 
…………………………………………（2分）木块向右运动到离A点最远时，速度为零，设木块向右移动最大距离为s1
解得 
…………………………（3分） 解得 
解得
………………………………………（2分） 
="0.60s," t2=
=0.40s ………………………………………（1分）木块向右减速运动的过程中相对传送带的位移为
， 产生的内能
……………………………………（2分）木块向左加速运动的过程中相对传送带的位移为
m，
……………………………………（2分）
…………………………………………………（2分）