大学MOOC 力学学科专业外语(西安科技大学)1451803171 最新慕课完整章节测试答案

Testsforweek3

1、单选题：
The three bars O1A, O2B and AB are pin-connected in one plane. At the position shown, O1A//O2B. In which case bar AB undergoes translation when bars O1A and O2B rotate in the plane.​
选项：
A:
B:
C:
D:
答案: 【 】

2、单选题：
Which statement is correct for a moving point?‏‎‏
选项：
A: If at is always equal to 0 and an is not equal to 0, then the point moves along a curve with varying speed.  
B: If at is constant and an is not equal to 0, then the point moves along a curve with uniformly varying speed.
C: If at is not equal to 0 and an is always equal to 0, then the point moves along a curve with varying speed.
D: If at is not equal to 0 and an is always equal to 0, then the point moves along a straight line with constant speed.
答案: 【 If at is constant and an is not equal to 0, then the point moves along a curve with uniformly varying speed.】

3、单选题：
A point moves along a curve with reducing speed. Which of the four drawings for the velocity and acceleration is possible?‍‌‍
选项：
A:
B:
C:
D:
答案: 【 】

4、单选题：
If a rigid body undergoes translation, then the motion path of a point on the rigid body‌​‌
选项：
A: must be a straight line.
B: must be a planar curve.
C: cannot be a spatial curve.
D: could be a spatial curve.
答案: 【 could be a spatial curve.】

5、单选题：
The velocities of two arbitrary points A and B on a rigid body are vA  and vB, respectively. Which statement is correct?‏‍‏
选项：
A: If the rigid body is in translation, then ½vA½=½vB½ must be satisfied.
B: If ½vA½=½vB½ is satisfied,  then the rigid body must be in translation.
C: If the rigid body is in translation, then ½vA½=½vB½ must be satisfied and the directions of the two velocities could be different.
D: If the rigid body is in translation, then the directions of vA and vB must be the same but probably |vA|¹|vB|.
答案: 【 If the rigid body is in translation, then ½vA½=½vB½ must be satisfied.】

6、单选题：
If a rigid body is rotating around a fixed axis, then‎‍‎
选项：
A: at some instant, the accelerations of all points on a line perpendicular to the axis of rotation are not parallel to each other.
B: at some instant, the velocity magnitudes of any two points are proportional to their vertical distances to the axis of rotation.
C: at some instant, the velocities of any two points are parallel to each other.
D: it is impossible that the motion paths of all points are circular arcs.
答案: 【 at some instant, the velocity magnitudes of any two points are proportional to their vertical distances to the axis of rotation.】

7、单选题：
The theorem of composition of velocities ​‍​
选项：
A: is only valid when the transport motion is a translation.
B: is only valid when the transport motion is a rotation.
C: is not valid when the transport motion is a rotation.
D: is valid for any type of transport motion.
答案: 【 is valid for any type of transport motion.】

8、判断题：
​​In composite motion of a point, the transport velocity and acceleration at an instant are the velocity and acceleration of the point in the moving reference frame coinciding with the moving point.​‏​
选项：
A: 正确
B: 错误
答案: 【 正确】

Testforweek8

1、单选题：
Based on the isotropy assumption, in all directions the material has the same ‌‎‌
选项：
A: stress
B: deformation
C: displacement
D: mechanical properties
答案: 【 mechanical properties】

2、单选题：
Which statement is correct?‎‍‎
选项：
A: The internal force on a cross section of a bar is the algebraic summation of the stresses on this cross section.   
B: The stress on a cross section of a bar is the average internal force on this cross section.  
C: Stress is the intensity of the internal force.
D: The internal force must be larger than the stress.
答案: 【 Stress is the intensity of the internal force.】

3、单选题：
The relationship between internal force and stress is that‏​‏
选项：
A: The internal force is smaller than the stress.
B: The internal force is the algebraic summation of the stress. 
C: The internal force is a vector and the stress is a scalar.               
D: The stress is the internal force per unit area. 
答案: 【 The stress is the internal force per unit area. 】

4、判断题：
The magnitude of the internal force of a bar depends on not only the external force but also the shape of its cross section.‏‏‏
选项：
A: 正确
B: 错误
答案: 【 错误】

5、判断题：
The stress is the intensity of the internal force per unit area.‌​‌
选项：
A: 正确
B: 错误
答案: 【 正确】

6、判断题：

The volume element deforms from the solid line position to the dash line position. The shear strain must be .

‌

‌选项：
A: 正确
B: 错误
答案: 【 错误】

Testforweek9

1、单选题：

The cross section area of a bar in tension is A. The normal stress  on the inclined plane with inclined angle  should be

‌

‍

‌选项：
A:
B:
C:
D:
答案: 【 】

2、单选题：

The axial load on section n-n of the bar should be

‌

‏

‌选项：
A: -3P
B: -4P
C: 4P
D: 8P
答案: 【 4P】

3、单选题：
For a