题干

如图所示,竖直向上的匀强电场中,绝缘轻质弹簧直立于地面上,上面放一个质量为m的带正电小球,小球与弹簧不连接。现将小球向下压到某位置后由静止释放,若小球从静止开始运动到离开弹簧的过程中,重力和电场力对小球做功的大小分别为和,小球离开弹簧时速度为v,不计空气阻力,则上述过程中        (      )

A:电势能增加

B:弹簧弹性势能最大值为

C:弹簧弹性势能减少量为+

D:机械能增加

上一题 下一题 0.0难度 选择题 更新时间:2019-11-13 09:13:36

答案(点此获取答案解析)

D

同类题5

阅读理解

    The booking notes of the play “Sherlock”

    Price: $10

    BOOKING

    There are four easy ways to book seats for the performance:

    in person

    The Box Office is open from Monday to Saturday, 10 am—8pm

    by telephone

    Ring 01324976 to reserve your tickets or to pay by credit card (Visa and MasterCard).

    by post

    Simply complete the booking form and return it to Box Office.

    --online

    Complete the online booking form at www.Satanfiedtheatre.com.

    DISCOUNTS:

    Saver: $2 off any seat booked any time in advance for performances from Monday to Thursday. Saver s are available for children up to 16 years old, over 60s and full-time students.

    Supersavers: half-price seats are available for people with disabilities and one companion. It is advisable to book in advance. There is a maximum of eight wheelchair spaces available and one wheelchair space will be held until an hour before the show.

    Standby: best available seats are on sale for $6 from one hour before the performance for people suitable for Saver and Supersaver discounts and thirty minutes before for all other customers.

    Group Booking: there is a ten percent discount for parties of twelve or more.

    School: school parties of ten or more can book $6 standby tickets and will get every tenth ticket free.

    Please note: we are unable to exchange tickets or refund money unless a performance is cancelled due to unforeseen circumstances.