问题
选择题
—What is the main cause of the accident?
—Driving _____.[ ]
A. careful
B. carefully
C. careless
D. carelessly
答案
答案:D
—What is the main cause of the accident?
—Driving _____.[ ]
A. careful
B. carefully
C. careless
D. carelessly
答案:D
小李在测定某滑轮组的机械效率时,得到下表中的两组数据。
序号 | 物重G/N | 提升重物高度h/m | 绳端拉力F/N | 绳端移动距离s/m | 机械效率η |
1 | 6 | 0.1 | 2.5 | 0.4 | 60% |
2 | 16 | 0.1 | 5 | 0.4 | 80% |
(2)比较两组实验数据可初步得出:使用同一滑轮组提升物体,物体所受的重力越大,滑轮组的机械效率越 (选填“高”或“低”) 。