问题 问答题

在一次课外活动中,某同学用图甲所示装置测量放在水平光滑桌面上铁块A与金属板B间的动摩擦因数.已知铁块A的质量mA=1kg,金属板B的质量mB=0.5kg.用水平力F向左拉金属板B,使其向左运动,弹簧秤的示数如图甲所示,则A、B间的摩擦力Fμ=______N,A、B间的动摩擦因数μ=______.(g取10m/s2).该同学还将纸带连接在金属板B的后面,通过打点计时器连续打下一系列的点,测量结果如图乙所示,图中各计数点间的时间间隔为0.1s,可求得拉金属板的水平力F=______N

答案

A处于平衡状态,所受摩擦力等于弹簧秤示数,Ff=F=2.50N.

根据Ff=μmAg,

解得:μ=0.25.

由题意可知,金属板做匀加速直线运动,根据△x=aT2

其中△x=2cm=0.02m,T=0.1s,

所以解得:a=2.0m/s2

根据牛顿第二定律得:F-Ff=mBa,

带入数据解得F=3.5N.

故答案为:2.50,0.25,3.50.

改错题

短文改错(共l0小题;每小题1.5分,满分l5分)

此题要求改正所给短文中的错误。对标有题号的每一行作出判断:如无错误,在该

行右边横线上画一个勾(√);如有错误(每行只有一个错误),则按下列情况改正:

此行多一个词:把多余的词用斜线(\)划掉,在该行右边横线上写出该词,并也用斜线划掉。

此行缺一个词:在缺词处加一个漏字符号(∧),在该行右边横线上写出该加的词。

此行错一个词:在错的词下划一横线,在该行右边横线上写出改正后的词。

注意:原行没有错的不要改。

Have you ever been bored with the busy life in the city?If so,    1.___________

have glimpse of the primary forest with me. The breathtaking       2.___________

scenery make you forget everything when you’re exploring what     3.___________

the forest has to offer. With thousands of trees surrounded            4.___________

you,you will feel like to floating on the green ocean. Under the      5.___________

leaves are all kinds of flowers,peacefully and shy. And a         6.___________

variety of birds were singing happily in the trees. While you’re      7.___________

enjoying the scenery on the ground,watching out for the sky!  8.___________

It will give your eye a feast. Wandering alone in the forest,  9.___________

we will have the feeling of returning to nature.            10.___________

多项选择题