皮皮学,免费搜题
登录
搜题
【简答题】
一辆小汽车正在匀速爬上六盘山一是1 000 m、坡高h是60 m的盘山路,小汽车的质量m是1 000 kg,小汽车的牵引力F是720 N.(计算结果保留两位小数) (1)如图所示,上山的路修成盘山弯曲的,目的是________. (2)如果小汽车上坡所用时间为60 s,求汽车牵引力做功的功率是多大? (3)这段盘山路的机械效率是多少?(取g=10 N/kg)
拍照语音搜题,微信中搜索"皮皮学"使用
参考答案:
参考解析:
知识点:
.
..
皮皮学刷刷变学霸
举一反三
【单选题】(单选)有一外径为18mm的无缝钢管,管内通冷冻盐水,为减少冷量损失,在管外包一层导热系数λ=0.18W/(m·°C)的石棉,保温层外壁与空气对流给热系数α=10W/(m2·°C),比较石棉厚为5mm和8mm时的冷量损失:
A.
5mm时损失较大
B.
8mm时损失较大
C.
一样大
D.
不好说
【单选题】(单选)有一外径为18mm的无缝钢管,管内通冷冻盐水,为减少冷量损失,在管外包一层热导率λ=0.18W/(m·℃)的石棉,保温层外壁与空气对流给热系数α=10W/(m2·℃),比较石棉厚为5mm和8mm时的冷量损失()*
A.
5mm 时损失较大
B.
8mm 时损失较大
C.
一样大
D.
不好说
【单选题】We found that the plane_____ when we got to the airport.
A.
already took off
B.
had already taken off
C.
was already taking off
D.
was already taken off
【单选题】构成敏感陶瓷的主要物质属于( )类。
A.
导体
B.
绝缘体
C.
半导体
【单选题】We have done things we ought not to have done and______ undone things we ought to have done.
A.
leave
B.
leaving
C.
left
D.
will leave
【单选题】What a pity ! Considering his ability and experience , he ____better. A . need have done B.must have done C. can have done D . might have done
A.
A . need have done
B.
must have done
C.
can have done
D.
D . might have done
【简答题】All that can be done _____. [     ] a. has done b. has been done c. have done d. have been done
【简答题】在“体检中心”页面,可以很醒目的看到目前店铺急需处理的()()()和待跟进申诉等。
【单选题】We have done things we ought not to have done and ________ undone things we oughtto have done.
A.
left
B.
leave      
C.
willleave      
D.
leaving
【单选题】构成敏感陶瓷的主要物质属于
A.
导体
B.
绝缘体
C.
半导体
D.
超导体
相关题目: