题目

如图所示，虚线a、b、c代表电场中三个等势面，相邻等势面之间的电势差相等，即 Uab=Ubc,实线为一带负电的粒子仅在电场力作用下通过该区域时的运动轨迹，P、Q是这条轨迹上的两点，不计粒子重力。则A.三个等势面中，a的电势最高                                         B.带电粒子在P点具有的电势能比在Q点具有的电势能大C.带电粒子通过p点时的动能比通过Q点时大                              D.带电粒子通过P点时的 　　Mark Twain was famous(著名)in his day as a public(公众的)speaker．In his public speeches(演说)he always liked to tell funny stories．He also liked to listen to funny stories and play jokes on his friends． 　　One day one of his friends lost his wallet(钱包)and asked Mark Twain to pay his train fare(车费)for him． 　　“But I don’t have enough money to pay both your fare and mine,”Mark Twain said．The friend didn’t know what to do． 　　“We can do this,”said Mark Twain．“We can get on the train and when the conductor comes to check the tickets(验票)，you can hide under my seat．” 　　Later, however, when the conductor came to check the tickets, Mark Twain gave him two tickets－one for his friend and one for himself ．Then he explained in a loud voice．“My friend here is a strange(奇怪的)man．When he travels on a train, he doesn’t like to sit on the seat．He prefers(宁愿)to lie on the floor under the seat．”Of course everybody in the train looked at the poor friend and laughed at him loudly． (1) The friend asked Mark Twain to buy a ticket for him because ________． [　　] A． he was too poor to buy one B． his wallet was lost C． his money was little D． Mark Twain had a lot of money (2) Mark Twain told him he couldn’t buy him a ticket because ________． [　　] A． he didn’t have enough money B． he wanted to play a joke on him C． he wanted to save some money D． he didn’t find his wallet, either (3) When the conductor came to check the tickets, the friend was ________． [　　] A． lying under the seat B． sitting on the seat C． lying on the seat D． standing nearby (4) Mark Twain spoke in a loud voice because ________． [　　] A． the conductor was standing far away B． his friend was deaf(聋) C． he enjoyed doing so D． he wanted all the people here to know there was a man under the seat (5) Which of the following sentences is not true? [　　] A． The friend didn’t know Mark Twain had bought a ticket for him． B． Mark Twain not only liked to tell funny stories but also liked to listen to funny stories． C． Both Mark Twain and his friend got on the train without a ticket． D． Mark Twain bought two tickets before they got on the train．