如习题2-14图（a)，（b)所示，两根杆A₁B₁和A₂B₂的材料相同，其长度和横截面面积也相

A . A B . B C . C D . D

A.t1=t2 B.t1&gt；t2 C.t1&lt；t2 D.无法确定

<img src='https://img2.soutiyun.com/ask/2020-08-24/967128400342044.png' /><img src='https://img2.soutiyun.com/ask/2020-08-24/96712841566392.png' /><img src='https://img2.soutiyun.com/ask/2020-08-24/96712843540805.png' />

<img src='https://img2.soutiyun.com/ask/2020-09-18/969313984906082.png' />

<img src='https://img2.51aidian.com/ask/2020-12-17/977086075083582.png' />

电路如练习题8-12图所示，已知u_s=100cos(20t)V。 (1)计算<img src='https://img2.soutiyun.com/ask/2020-08-28/967470801948578.png' /> (2)绘相量图表面(1)中各相量; (3)求<img src='https://img2.soutiyun.com/ask/2020-08-28/967470841053815.png' />的相位关系; (4)写出i、u_ab、u_bc及u_cd。 <img src='https://img2.soutiyun.com/ask/2020-08-28/96747081020605.png' />

<img src='https://img2.soutiyun.com/ask/5169001-5172000/85cac9e3bee9bf7fc1eae10a387d4ccf.jpg' />

<img src='https://img2.soutiyun.com/ask/2021-01-19/97991528204874.jpg' />

电路如题1-11图所示，试求(1)图(a)中电流i₁和电压u_ab;(2)图(b)中电压u_cb。 <img src='https://img2.soutiyun.com/ask/2020-08-20/966768174350855.png' /><img src='https://img2.soutiyun.com/ask/2020-08-20/966768181740278.png' />

按整数因子D=4抽取器原理方框图如题3图(a)所示。其中，F_x=1kHz，F_y= 250Hz，输入序列x(n)的频谱如题3图(b)所示。请画出题3图(a)中理想低通滤波器h_D(n)的频率响应特性曲线和序列v(n)、y(m)的频谱特性曲线。 <img src='https://img2.soutiyun.com/ask/2020-09-11/968693529713581.png' />

<img src='https://img2.soutiyun.com/ask/2020-07-17/963826915724713.png' />

在直径D=8a的圆截面中，开了一个2ax4a的矩形孔，如习题1-15图(a)所示。试求截面对其水平形心轴和竖直形心轴的惯性矩I_x，和I_y。 <img src='https://img2.soutiyun.com/ask/2020-09-10/968602511055483.png' /> 习题1-15图

习题9-16图(a)所示结构中钢梁AB及立柱CD分别由16号工字钢和连成一体的两根63mmx63mmx5mm角钢制成，杆CD符合钢结构设计规范中b类截面中心受压杆的要求。均布荷载集度q=48kN/m。梁及柱的材料均为Q235钢，[σ]=170MPa，E=210GPa。试校核梁和立柱是否安全。 <img src='https://img2.soutiyun.com/ask/2020-09-10/968596665304097.png' />

<img src='https://img2.soutiyun.com/shangxueba/ask/50796001-50799000/50796740/967040986097027.png' />

<img src='https://img2.soutiyun.com/ask/2020-09-01/96781572451352.png' />

半径R=100mm的圆盘绕其圆心转动，图7-12a所示瞬时，点A的速度为v_a=200jmm/s，点B的切向加速度<img src='https://img2.soutiyun.com/ask/2021-03-01/983460973982692.png' />。求角速度ω和角加速度α，并进一步写出点C的加速度和矢量表达式。 <img src='https://img2.soutiyun.com/ask/2021-03-01/983460984520295.png' />

<img src='https://img2.soutiyun.com/ask/2021-03-02/983551408663457.png' />

电路如练习题8-13图所示，已知i_s(t)=cos(t+90°)A，试求稳态电压u(t)，并绘相量图。 <img src='https://img2.soutiyun.com/ask/2020-08-28/967470947804921.png' />

<img src='https://img2.soutiyun.com/ask/2021-02-20/982709794204926.png' />

分别判断图P2.2(a)、(b)所示两电路各属哪种放大电路,并写出Q、A_u、R_i和R₀的表达式. <img src='https://img2.soutiyun.com/ask/2021-01-09/979034368257886.png' /> <img src='https://img2.soutiyun.com/ask/2021-01-09/979034378158452.png' />

电路如图6-2(a)所示，图(b)为电感电压的波形图，已知R=10Ω，L=4 H，电感电流i_L(0)=0，求电流i_L(t)。 <img src='https://img2.soutiyun.com/ask/2020-08-23/967073690265931.png' />

假定练习题4-3图(a)所示电路中，器件A的伏安特性曲线如练习题4-3图(b)所示.试求在下列三种情况下10Ω电阻的电压： <img src='https://img2.soutiyun.com/ask/2020-08-24/967136242730603.png' /><img src='https://img2.soutiyun.com/ask/2020-08-24/967136250058022.png' /> <img src='https://img2.soutiyun.com/ask/2020-08-24/967136258148485.png' /> (1)Us=2V时; (2)Us=1/2V时; (3)Us=-2V时。

平面力系向题3-15图(a)所示坐标系A，B和C三点简化，主矩分别为M_A=20N·m, M_B=0，M_C=-10N·m。求该力系合力的大小，方向和作用线方程。坐标单位为m。 <img src='https://img2.soutiyun.com/ask/2020-12-08/976298875450058.png' />

密闭盛水容器如[例87]图(a)所示,已知h₁=0.6m,h₂=1.0m,水银测压计测得△h=0.25m,试求半径R=0.5m的半球形盖AB所受总压力的水平分力和垂直分力. <img src='https://img2.soutiyun.com/ask/2020-09-23/969715549817315.png' /> [例87]图