问题 问答题

(1)用螺旋测微器测量金属丝的直径,示数如图1所示,读数为______mm.用游标为20分度的卡尺测量小球的直径,示数如图2所示,读数为______cm.

(2)某同学用打点计时器测量做匀加速直线运动的物体的加速度,电源频率f=50Hz,在纸带上打出的点中,选出零点,每隔4个点取1个计数点.因保存不当,纸带被污染,如图所示,A、B、C、D是依次排列的4个计数点,仅能读出其中3个计数点到零点的距离:SA=16.6mm、SB=126.5mm、SD=624.5mm.

若无法再做实验,可由以上信息推知:

①相邻两计数点的时间间隔为______s;

②打C点时物体的速度大小为______m/s(保留两位有效数字);

③物体的加速度大小为______(用SA、SB、SD和f表示).

答案

(1)螺旋测微器的固定刻度读数为0.5mm,可动刻度读数为0.01×11.8mm=0.118mm,所以最终读数为:0.518mm,由于需要估读因此在范围0.517-0.519内均正确,

游标卡尺的固定刻度读数为0.6cm,游标读数为0.05×15mm=0.75mm=0.075cm,所以最终读数为:0.6cm+0.075cm=0.675cm.

故本题答案为:0.518(0.517-0.519),0.675.

(2)①打点计时器打出的纸带每隔4个点选择一个计数点,则相邻两计数点的时间间隔为:5T=0.1s.

②根据间的平均速度等于点的速度得vc=

xBD
2T
=2.5m/s.

③匀加速运动的位移特征是相邻的相等时间间隔内的位移以aT2均匀增大,即△x=aT2,所以有:

xBC=xAB+aT2

xCD=xBC+aT2=xAB+2aT2

xBD=2xAB+3aT2

所以:a=

(sD-sB)-2(sB-sA)
3T2
=
(sD-3sB+2sA)f2
75

答案:①0.1;②2.5;③

(sD-3sB+2sA)f2
75

填空题
根据短文内容,选择适当的单词或短语填空,使短文意思完整。每个选项至多使用一次,有两项剩余。

refused,    between,    led,    earlier,    warm     agreed,    later,    family,    but,    failed,    dog,    food

     Brownie and Spotty were neighbor dogs. They loved each other and played together so often that they had
made a path (小路) through the grass of the field 1______ their houses.
     One evening Brownie's family noticed that Brownie didn't return home. They went looking for him 2______.
Brownie didn't show up the next day, and the next week.
     Spotty went to Brownie's house alone. He barked loudly. But Brownie's 3______ were too busy to care about
him. Finally, one morning Spotty 4______ to take "no" for an answer. He followed Ted,Brownie's owner, every
where he went. He barked, then rushed toward a nearby empty place and back, as if to say. "Follow me!"
     Finally, Ted followed the dog across the empty place. The little dog 5______ the man to a tree half a mile
from the house. There Ted found Brownie alive one of his legs was crushed (压住) in a trap (老鼠夹). Ted
wished he had come 6______. Then Ted noticed that, in a circle around the injured dog, a lot of 7______ was
left over after lots of meals.
     Spotty had been visiting Brownie every day. He had stayed with Brownie to protect him, snuggling (依偎)
with him at night to keep him 8______ and nuzzling (用鼻子爱抚) him to keep his spirits up.
问答题