2020 力学学科专业外语(西安科技大学) 最新满分章节测试答案

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本课程起止时间为:2020-03-04到2020-05-20
本篇答案更新状态:已完结

05 Composite motion of a point Tests for week 3

1、 问题: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、 问题: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、 问题: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、 问题: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、 问题: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、 问题: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、 问题: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、 问题: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】

13 Strain Test for week 8

1、 问题: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、 问题: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、 问题: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、 问题: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、 问题: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、 问题: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】

15 Axial load Test for week 9

1、 问题: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、 问题: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、 问题:For a bar under axial tension, the sections with the maximum normal stress and maximum shear stress are
选项：
A:the cross section and inclined section with inclined angle 45°, respectively.
B:both the cross sections.
C:the inclined section with inclined angle 45°and cross section, respectively.
D:both the inclined sections with inclined angle 45°.
答案: 【the cross section and inclined section with inclined angle 45°, respectively.】

4、 问题:Hooke’s law can be used for
选项：
A:ductile materials only.     
B:axial tension only.
C:a case with the stress smaller than the proportional limit.
D:a case with the stress smaller than the yielding stress.
答案: 【a case with the stress smaller than the proportional limit.】

5、 问题:After strain hardening (cold hardening), the material shows
选项：
A:higher proportional limit and lower ductility.
B:higher proportional limit and ductility.
C:lower proportional limit and higher ductility
D:lower proportional limit and ductility.
答案: 【higher proportional limit and lower ductility.】

6、 问题:The maximum tensile force in the bar should be
选项：
A:12KN
B:20KN
C:8KN
D:13KN
答案: 【20KN】

7、 问题:The tensile rigidity of the bar with length 2l is EA. The total elongation of the bar should be
选项：
A:
B:
C:
D:
答案: 【】

8、 问题:The bar is subjected to a force as shown. One end of the bar is fixed. Which statement is correct?
选项：
A:There is no deformation in segment AB.
B:There is no deformation in segment BC.
C:There is no displacement for any cross section in segment AB.
D:There is no displacement for any cross section in segment BC.
答案: 【There is no deformation in segment BC.】

9、 问题:The bar with a slot in segment BC is subjected to tensile loading. Which of the following is correct for the axial forces and stresses in segment AB and BC?
选项：
A:
B:
C:
D:None of these is correct.
答案: 【】

10、 问题:If the total elongation of a bar is zero, then there must be no displacement for each cross section of the bar.
选项：
A:正确
B:错误
答案: 【错误】

11、 问题:Two bars made of two different materials have the same length and cross section area. If the axial loads in the two bars are the same, then the stresses on their cross sections must be also the same.
选项：
A:正确
B:错误
答案: 【正确】