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查看答案和解析>>

一、选择题

1

2

3

4

5

6

7

8

9

10

11

12

D

ABC

ABD

AC

A

AC

BC

AC

AD

C

C

C

二、填空题

13.   14.4m                       14.(M+m)g-masinθ    15. 0.5s   18.75m或75/4

16.2.5m/s²                       17.1.5gsinα

三、计算题

18. 甲→V_甲=1.5m/s     乙→V₂=10m/s                                                                         (1)s=25m<L       

 A=o.5m/s²                                                                                                                                                           (2)s=25m=L

考虑两车速度相等时的相对位移S                                                                          (3)s=25m>L

2as=(15-10)²

∴s==25m

19.

(1)   对B有s=a₁t²        ∴a₁=

(2)   对B受力分析由牛顿第二定律的F-f=m_B?a₁⇒f=45N

∴              

∴v_A=a_A?t=4.5m/s

(3)   ∆S=S_B-S_A=5-a_A?t²=0.5m

20.

对B:                        t₁=

对A:                        v₁=a₁?t₁=μg?

A再次与B相对静止t₂=

∆S=S_B-S_A=

21.(1)N_A=mgcosθ

22.

F-μ(m₁+m₂)g=(m₁+m₂)a₁⇒a₁=1m/s²

a₂=μg=1m/s²                                             a₃=

(a₁t₁)(6-t₁)+ a₃(6-t₁)²=18                       ⇒  t₁=(6-6)s

V=a₁t₁+a₃(6-t₁)=(18-6)m/s