首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Narrator Listen to part of a discussion in a physics class. The professor is discussing Forces. Now get ready to answer
Narrator Listen to part of a discussion in a physics class. The professor is discussing Forces. Now get ready to answer
admin
2013-04-25
24
问题
Narrator
Listen to part of a discussion in a physics class. The professor is discussing Forces.
Now get ready to answer the questions. You may use your notes to help you answer.
What does the professor mean when he says this?
Professor Well, today we’d talk about Force and its representation.
Student A So what is force?
Professor Well, actually, a force is a push or pull upon an object resulting from the object’s interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. When the interaction ceases, the two objects no longer experience the force. Forces only exist as a result of an interaction.
Student A interrupting
You mean if a force exists, there should be two objects. Am I right?
Professor That’s right. Er, ...For simplicity sake, all forces, interactions, between objects can be placed into two broad categories. One is contact force; the other is force resulting from action-at-a-distance.
Student B interrupting
Action-at-a-distance?
Professor Yeah, first let’s talk about contact force. Contact forces are types of forces in which the two interacting objects are physically in contact with each other. Examples of contact forces include frictional forces, tensional forces, normal forces, air resistance forces, and applied forces. These specific forces will be discussed in more detail later in Lesson 2, as well as in other lessons.
Student A Uh...so many forces fall into this category. Then, what is "force resulting from action-at-a-distance"?
Professor Er Action-at-a-distance forces are types of forces in which the two interacting objects are not in physical contact with each other, yet are able to exert a push or pull despite a physical separation. Examples of action-at-a-distance forces include gravitational forces, such as, the sun and planets exert a gravitational pull on each other despite their large spatial separation; even when your feet leave the earth and you are no longer in contact with the earth, there is a gravitational pull between you and the Earth. Next, electric forces, such as, the protons in the nucleus of an atom and the electrons outside the nucleus experience an electrical pull towards each other despite their small spatial separation; and magnetic forces, for example, two magnets can exert a magnetic pull on each other even when separated by a distance of a few centimeters. These specific forces will be discussed in more detail in other lessons.
Student B That’s magic! I am quite familiar with the phenomenon you mentioned just now, but before this class, I had no concept of these categories of forces.
Student A Er, I know very little about this, too.
Professor Actually, forces exist in our daily life. Force is a quantity which is measured using the standard metric unit known as the Newton. A Newton is abbreviated by an "N". To say "10.0 N" means 10.0 Newtons of force.
Student A interrupting
So Newton is the standard metric unit of force?
Professor That’s true. In fact, a force is a vector quantity. As we learned in an earlier unit, a vector quantity is a quantity which has both magnitude and direction. To fully describe the force acting upon an object, you must describe both the magnitude and the direction. Thus, "10 Newtons" is not a full description of the force acting upon an object. In contrast, "10 Newtons downwards" is a complete description of the force acting upon an object; both the magnitude, "10 Newtons", and the direction, "downwards", are given.
Student B Uh, that’s quite complex and easy to make a mistake.
Professor Yeah because a force is a vector which has a direction, it is common to represent forces using diagrams in which a force is represented by an arrow. Such vector diagrams were introduced in an earlier unit and will be used throughout your study of physics. The size of the arrow is reflective of the magnitude of the force and the direction of the arrow reveals the direction which the force is acting. Such diagrams are known as free-body diagrams. Furthermore, because forces are vectors, the influence of an individual force upon an object is often canceled by the influence of another force. For example, the influence of a "20 Newton upward" force acting upon a book is canceled by the influence of a "20 Newton downward" force acting upon the book. In such instances, it is said that the two individual forces "balance each other", meaning there would be no unbalanced force acting upon the book.
Student A That sounds interesting. Then, there should be other situations in which two of the individual vector forces cancel each other, the so-called balance, yet a third individual force exists that is not balanced by another force.
Professor That’s the point. Next time we will learn how to draw the free-body diagrams, which can help you to understand the situation more easily.
选项
A、He thinks the student’s view is quite right.
B、He thinks the student’s opinion is wrong.
C、He is not sure about the student’s opinion.
D、He does not want to give his own opinion.
答案
A
解析
本题为语用理解题,考查考生是否理解说话者说话的目的。题目问:为什么教授说“That’s the point”?他说学生说的正是要点,是在赞成学生的说法,即赞成“Then there should be other situations in which two of the individual vector forces cancel each other, the so-called balance, yet a third individual force exists that is not balanced by another force”,因此选择A。
转载请注明原文地址:https://kaotiyun.com/show/T7yO777K
0
托福(TOEFL)
相关试题推荐
Completethesummarybelow.UseNOMORETHANTHREEWORDSforeachanswer.PROJECTMANAGENTLastweek’sdefinitionofpro
Completethesummarybelow.UseNOMORETHANTHREEWORDSforeachanswer.PROJECTMANAGENTLastweek’sdefinitionofpro
CompletethefollowingnotesusingNOMORETHANTHREEWORDSforeachanswerIfrobbed,youshouldcontactyour【16】orDarling
Completethefollowingsentences.UseNOMORETHANTHREEWORDSforeachanswer.Thespeakeridentifiesthefollowingtwo
Labelplanbelow.ChooseyouranswersfromtheboxbelowandwritethelettersA-Hnexttoquestions17-20.A.AvocadoP
"ResearchMethodology"Closescientificmethodbasedonempiricalevidence(=(21))Findaresearchproblemorques
Completethenotesbelow.WriteNOMORETHANTWOWORDSforeachanswer.AgricultureandEnvironment(31)productio
SECTION1Questions1-10Questions1-4CompletethefollowinginformationusingNOMORETHANTHREEWORDSAND/ORNUMBERSfore
STUDENTBANKINGNote:Maynotbeallowedallfacilitiesgiventoresidentstudents.FundingMustprovide【T14】______.Icans
Choosethecorrectletter,A,BorC.WinridgeForestRailwayParkWhentheystarted,thefamilydecidedto
随机试题
关于剂型的分类,下列叙述错误的是()。
依照现行相关法律法规的规定,纳入区域性开发的建设项目,在( )情况下,经有审批权的环境保护行政主管部门同意后,环境影响评价工作可适当简化。
下列哪种说法是错误的?()
——Canyoutellme____?——Bydoingmorespeaking.
你是单位办事大厅负责人,你们单位大厅人员一直都勤勤恳恳工作,到年底接受群众评价的时候,还是有很多群众评价不满意,单位大厅的工作人员很沮丧。作为负责人,你会怎么办?
(2016年第3题)某资本家投资100万元创办企业从事生产,60万元用于固定资本、以购买机器设备等,40万元用于流动资本、以购买原材料和劳动力等(其中购买劳动力支付了10万元)。一轮生产结束后,该企业的总资本达到了120万元。那么,该企业的剩余价值率为
ThomasR.SmithDriversCo.3489GreeneAve.Olympia,WA98502DearMr.Smith,Iwasvery(141)toreadyourletterofAugust1
Oneofthebiggestchallengesfacingemployersandeducatorstoday【C1】______therapid【C2】______ofglobalization.Themarketplac
I______writingthepaperasscheduled,butmymother’sillnessinterfered.Ihopeyouwillexcuseme.
WhatdoestheinterviewerfindsurprisingaboutMariella’shouse?
最新回复
(
0
)