问题 计算题

如图,光滑水平面上存在水平向右、场强为E的匀强电场,电场区域宽度为L。质量为m、带电量为+q的物体A从电场左边界由静止开始运动,离开电场后与质量为2m的物体B碰撞并粘在一起,碰撞时间极短。B的右侧拴接一处于原长的轻弹簧,弹簧右端固定在竖直墙壁上(A、B均可视为质点)。求

(1)物体A在电场中运动时的加速度大小;

(2)物体A与B碰撞过程中损失的机械能;

(3)弹簧的最大弹性势能。

答案

(1)  (2) (3)

题目分析:(1)小球受到合外力为F=qE                 (2分)

                 (2分)

(2)小球离开电场时的速度为v

             (2分)

A、B碰撞过程中,系统机械能守恒

                               (2分)

碰撞过程中损失的机械能为

则:                           (2分)

解得:                        (2分)

(3)由能量守恒得:

                     (4分)

阅读理解

Recreational tree climbing is taking root in the ecotourism industry, and it's sending guys like Tim Kovar to far off reaches of the globe. Kovar, a tree-climbing instructor, recently returned to the U.S. from Brazil, where he spent time developing a tree-climbing operation thanks to the "slow travel" movement.

Slow travel, is like the slow food movement, the practice of giving fast food in favor of homegrown cooking—the kind that takes hours to prepare and enjoy. Likewise, slow travel urges visitors to experience a place's natural surroundings and learn about the ecology in a way not afforded by extreme games.

"Tree climbing is a slow activity," says Kovar. "It's not something you do quickly and then you're on to the next thing or event." There is no such thing as a quick climb, especially for beginners. This wasn't a race against the clock or the fellow climbers. In fact, tree climbing is unlikely to ever become a feature of the extreme games. Many climbers refuse competition. There has already been so much competition in the world.

"When you stand below the tree, it can be amazing," Rusel DeMaria says, looking affectionately up at Michael's Triumph, a 150-foot-tall tree. But reaching the treetop, he adds, is an entirely different feeling. Likewise, his wife, Viola Brumbaugh, kneels on the ground and asks Michael's Triumph for permission to climb. "It goes a lot smoother that way, "She says.

And climbing has been included into many educational programs. New Tribe offers guided climbs through its school, Tree Climbing Northwest, where "we teach enough tree biology and forest ecology to raise awareness in our students," says New Tribe present Sophis Sparks. "We know that the tree climbing experience deepens personal appreciation for trees. After climbing, people value trees more and are motivated to support preservation. This is not just to preserve their playground."

Perhaps that is why he struggles with the term "recreational tree climbing," saying, "I prefer to call it inspirational tree climbing."

小题1:What do slow travel and the slow food movement have in common?

A.They take people a long time.

B.They are related to the eco-tourism industry.

C.They advocate protecting nature.

D.They cost people little money小题2:What do we know about tree climbing from the passage?

A.People compete to see who can climb to the top first.

B.It favors the experience of enjoying nature.

C.It is a kind of extreme sport and needs a lot of effort.

D.People view it as a challenge to climb the tallest tree in a forest.小题3:Brumbaugh kneels on the ground before climbing trees to ___________________.

A.beg for the safety of climbing

B.Expect to climb faster than her husband

C.Show respect for the tree

D.ask for permission of her husband小题4:Sophia Sparks prefers the term "inspirational tree climbing" because it ____________.

A.provide people with more chances to play outside

B.bring a lot of pleasure to life

C.Deepens personal love between each other

D.Makes people realize they should protect trees小题5:What's the best title for the passage?

A.Tree-climbing travelling

B.Slow travel movements

C.Dangers of climbing

D.Respect for nature

单项选择题