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【简答题】

质量为 m=70kg的撑杆运动员从 h=5.0m高处落到海绵垫上,经Δ t 1=1s后停止,则该运动员身体受到的平均冲力为___________N,如果是落到普通沙坑中,经Δ t 2=0.1s停下,则沙坑对运动员的平均冲力为________________N(取g=10m/s 2).

题目标签:海绵垫普通冲力
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【单选题】第二篇 Pushbike Peril Low speed bicycle crashes can badly injure—or even kill—children if they fall onto the ends of the handlebars (车把). So a team of engineers is redesigning the humble h...

A.
it is not easy to persuade manufacturers to adopt the new design.
B.
the team of engineers has not found any countermeasures.
C.
children like to ride bicycles at a very low speed.
D.
a lot of children were killed in bicycle accidents in the past 30 years.

【单选题】(2005年)要用冲床在厚度为t的钢板上冲出一圆孔,则冲力大小( )。

A.
与圆孔直径的平方成正比
B.
与圆孔直径的平方根成正比
C.
与圆孔直径成正比
D.
与圆孔直径的三次方成正比

【单选题】普通电磁继电器由( )和触点组成。

A.
铁心
B.
衔铁
C.
永久磁铁
D.
电磁铁
E.
程度:中

【单选题】急性普通型肝炎的病变特点是

A.
以肝细胞变性为主
B.
以肝细胞坏死为主
C.
以汇管区渗出为主
D.
以肝细胞增生为主
E.
以汇管区间质增生为主