物理答案及评分标准
一、二:选择题
题号 1 2 3 4 5 6 7 8 9 10 11 12
答案 C A D C D B A BC CD AC BC AB
三、解答题
13.84.50 80.0 无影响 ......................................................................每空 2分
2
14. C 0.388 斜面倾角过大 .......................................................每空 2分
M
15.(9分)【答案】(1)25N,15N;(2)0.25
【详解】(1)对 O点进行受力分析可知
T cos37o mg ..............................................................................................................2分D
T sin 37o T .................................................................................................................2分D B
代入数据可得 DO,BO线的拉力大小分别为
T 25N ...........................................................................................................................1分D
TB 15N ............................................................................................................................1分
(2)由于整个系统恰好处于静止状态,则
TA Mg ..........................................................................................................................2分
解得 0.25 .....................................................................................................................1分
1
16(9分)(1) h gt 2 ..............................2分
2
得: t 2s ........................................1分
v gt .........................................2分
得: v 20m / s ......................................1分
(2)由题意知,窗口的高度为: h 2m
1
h v1 t g t
2
......................................2分
2
v1 9m s ......................................1分
17(9分)(1)设最大速度为vm ,匀速阶段所用时间为 t2,根据题意有:
t t1 t2 12s ................................................................................................................1分
x v m1 t1 16m ..............................................................................................................1分2
试卷第 1页,共 3页
x2 vmt2 64m ......................................................................................1分
联立解得:
t1 4s ..............................................................................................................................1分
vm 8m / s ......................................................................................................................1分
(2)小明匀加速运动阶段的加速度大小为
a v m 2m / s2
t .............................................................................................................1分1
根据牛顿第二定律可得,对 m有
N cos37° f sin 37° mg ............................................................................................1分
N sin 37° f cos37° ma .............................................................................................1分
联立解得:
N 9.2N .....................................................................................................................1分
18(11分)解:(1)设物块的加速度大小为 a1,由牛顿第二定律有
1mg ma1 .......................................................................................................................1分
解得:
a1 1g 2m / s
2 .............................................................................................................1分
因为 2s时达到共速,此时速度大小:
v1 v0 a1t1 2m / s ........................................................................................................1分
长木板由静止做匀加速直线运动,加速度大小:
a v12 1m / s
2
t ................................................................................................................1分1
(2)对长木板由牛顿第二定律有:
1mg 2 m M g Ma2 .............................................................................................1分
解得:m 4kg ..............................................................................................................1分
2s内物块对地位移大小为:
x v0 v11 t1 8m2
2s内长木板对地位移大小为:
x v2 1 t1 2m2
则 t 2s时物块到长木板左端的距离为:
试卷第 2页,共 3页
d x1 x2 6m ...............................................................................................................1分
(3)共速后,对物块和长木板整体,由牛顿第二定律有:
2 m M g (m M )a3 ..........................................................................................1分
a 1m / s2解得: 3 ................................................................1分
与挡板碰撞前瞬间,整体具有速度:
v2 v1 a3t2 ....................................................................................................................1分
可得: v2 1.5m / s
碰撞后,物块 m运动到停下有:
0 v 22 2a1s
解得: s 0.56m L d 0.5m
因此,物块会脱离长木板
v2 v 22 2a1(L d )
解得: v 0.5m / s …...............................................................................................1分
试卷第 3页,共 3页