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问题 选择题

如图所示，光滑曲面的两端A、B离地面的高度分别为H和h，一小球自A端由静止释放沿曲面下滑并经过B端飞出落地，则小球经过B端时的速率与刚落地时的速率之比为（　　）

A．

h
H

B．

H-h
H

C．

H-h
H

D．

H-h
h

答案

小球运动的过程中，只有重力做功，机械能守恒，则得：

从A到B过程，有：mgH=mgh+

1
2
m
v2B
，得 vB=
2g(H-h)

从A到地过程，有：mgH=

1
2
m
v2地
，得 v地=
2gH

所以有：

vB
v地
=
H-h
H

故选：C

问答题

Yado Steel Co Ltd (Yado Steel) entered into a loan agreement with Industry Bank to borrow RMB 20 million yuan for its expansion programme. Yado Steel provided its office building as property mortgaged for the debt, and made the registration as required. Mr Ding, one of the shareholders of Yado Steel, placed a guarantee letter of general liability in favour of Industry Bank.Due to poor performance, Yado Steel failed to repay the debt when it came to maturity. Meanwhile, Industry Bank, under a restructuring plan, transferred the credit of RMB 20 million yuan together with the right of pledge to Oriental Assets Management Co (OAM). It also made a written notice to Yado Steel and Mr Ding, but failed to transfer the right of mortgage to OAM. On the contrary, Industry Bank concluded an agreement with Yado Steel before it went bankrupt, and settled other debts owed by the latter through the sale of the office building as mortgaged for the loan. Having found this fact, OAM, as a transferee of the credit, requested the court to order Mr Ding to bear its guarantor’s liability for the debt. Mr Ding asserted that he was a pledger with a general liability and would be responsible for the debt only if the things mortgaged could not satisfy the debt.Required:Answer the following questions in accordance with the relevant provisions of the Property Law and the Contract Law, and give your reasons for your answer:

(b) State what was the cause of this dispute between OAM and Industry Bank. (4 marks)
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选择题
如图所示，AB是一质量为m的均匀细直杆，A端靠在光滑的竖直墙壁上，B端置于水平地面上，杆身与竖直方向夹角为θ，杆与地面的摩擦系数为μ，保持平衡，则此时杆与地面的摩擦力为（　　）

A．mgtgθ

B．mgsinθ

C．μmg

D．μmg
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