问题 问答题

质量为100kg的方形木箱,在水平推力的作用下,在水平面上做匀速直线运动.若箱子受到的摩擦力只有其重力的0.2倍,求箱子受到的水平推力.g取10N/kg.

答案

(1)∵物体质量为100kg;

∴根据G=mg可得:物体受到的重力为:G=mg=100kg×10N/kg=1000N.

(2)因为木箱做匀速直线运动

所以推力F=f=0.2G=1000N×0.2=200N.

答:箱子受到的水平推力为200N.

完形填空

Recently a group of second-graders visited our school library to work on a “holidays around the world” project. The children created pictures showing holiday customs and then created voice recordings explaining what they drew.    小题1:   Now imagine taking things one step further and creating Podcasts in a classroom setting.

The term Podcast refers to an audio recording, linked to the Web, that can be downloaded to a personal MP3 player. The word is created from broadcast and from iPod—the wildly popular MP3 player from Apple.

Using audio with students isn’t new, of course. Teachers have used audiobooks at listening centers and recorded student voice on tape or CD for many years.    小题2:   Podcasts, however, can reach a much wider audience in a time frame outside the school days. Booktalking, an old way of getting kids excited about books, gets a tech assistance with Podcasting. Students can do some booktalking themselves; book review Podcasts seem to be another natural way for students to share what they know, providing an alternative to the book report.

 小题3:  Teachers made audio Podcasts, including visuals or video clips for any content area instruction and review. Some teachers have begun to record themselves teaching important concepts; this creates an account of information online for kids to access when they’re stuck on a homework assignment.   小题4:   Imagine being a classroom teacher in September who can actually hear how his or her students were reading in June the school year before.

You don’t need an iPod to make a Podcast.    小题5:  While an MP3 player is a popular and useful gadget, your audience doesn’t need MP3 players to listen, either. Your students and their families can use the computer to play back what you’ve recorded.

A.Audio and video files can also function as assessment tools.

B.It is clearly showed in the incident that student-created voice recordings are effective.

C.Podcasting is of vital importance to the classroom setting.

D.Podcasting is used for various excellent reasons.E. You can make a Podcast if you have a computer, a microphone, and some free software.

F. Podcasting needs a variety of devices.

G. Voice and music have been seen as the original media for teaching.

单项选择题