问题 计算题

某物理课外小组想探究“带风帆的玩具小车所受阻力与运动速度的关系”,他们进行了以下实验探究:

(1)猜想:①f与车的速度v无关;②;③

(2)探究步骤

①将带有风帆的玩具小车、已连接好电源的打点计时器和纸带按如图10甲所示安装在光滑倾斜的长木板上;

②接通打点计时器电源(电源频率f=50Hz),使玩具小车从静止开始加速运动,足够长的时间后关闭打点计时器;

③改变长木板的倾角,重复以上实验,记录实验数据如下表所示:

实验次数木板倾角θsinθ小车匀速运动时的速度vm/s小车匀速运动时速度的平方v2m/s2
10.070.600.36
210°0.18 ×
324°0.413.5112.32
436°0.595.0625.60
548°0.746.3440.20
660°0.87 ×
请你根据该小组的探究完成下列的问题:

(Ⅰ)图10乙是倾角θ=10°的一条打点纸带,通过计算完成表中对应的空白项;

(Ⅱ)通过观察表中的实验数据,试将θ=60°时小车匀速运动的速度填在表中对应的空白处.

(Ⅲ)结论:在实验误差范围内,通过对数据的观察分析,玩具小车所受的阻力与运动        速度的定性关系是                               .也可以进一步通过图象法对数据进行分析得到运动小车所受到阻力与运动速度的定量关系.

答案

(Ⅰ)1.50m/s

(Ⅱ)7.40m/s~7.50m/s

(Ⅲ)小车所受阻力与速度成正比(fv

(Ⅰ)考查小车在斜面倾角θ=10°下滑时打出一条打点纸带,选取小车匀速运动时打下的记数点,通过公式v=x/t求出速度v。此问主要考查考生处理纸带数据的能力。

(Ⅱ)主要考查考生通过观察表中的实验数据,运用推理、比较的思想和方法得出当斜面θ=60°时小车匀速运动的速度的大小。

(Ⅲ)主要考查通过推理、观察分析实验数据得出玩具小车所受的阻力与运动速度的定性关系。

单项选择题
单项选择题

School authorities often refuse to face the problem of drug-abuse; government drug-abuse agencies have done too little to inform the public about it; many physicians still seem unaware of it when they examine teenagers. As a result, parents may still be the last to know that their children have fallen victim to the drug epidemic that has been raging for more than a decade among American’s youth. In a survey of a middle-income Cincinnati suburb, 38 percent of the sixth grade and 89 percent of the senior class said they used drug and alcohol; 48 percent of the parents thought their children used alcohol, but only 8 percent thought their children used drug.

Fortunately, there is a new force at work against this epidemic—a nationwide movement of more than 400 parent groups formed to expose and battle drug use among teenagers and preteens. The groups have different approaches and widely varying rates of success. Yet this parental crusade is the only major force in the country to have taken active, organized and effective steps aimed at stopping marijuana use.

Why the concentration on marijuana Marijuana is the illegal drug most used by kids. According to a National High School Survey, 44 percent of U. S. high school seniors had smoked pot during their school years, and one out of seven of these were daily or near daily smokers. There was a close-related connection between pot smoking and subsequent use of cocaine and heroin by young men. Of those who had smoked pot fewer than 100 times, seven percent had graduated to cocaine, four percent to heroin. But of those who had smoked pot at least 1,000 times, 73 percent had gone on to cocaine, and one out of three had graduated to heroin.

Parent groups have found that by stopping their kids from smoking pot, they almost automatically stop all other illegal drugs, and cut down on alcohol use as well. The High School Senior Survey’s statistics show that heavy pot smokers tend to be heavy drinkers, while those who do not use pot tend not to drink heavily.

Since virtually all over the country teenage " partying " has come to mean " getting smashed and getting stoned " on anything from pot to pills to hashish, LSD, and alcohol, some parent groups home in on the partying aspect. Parents Who Care (PWC) was started in 1979 by 15 Palo Alto, Calif., parents who were upset by stories of serious drug problems at parties. They held talk sessions with their children and learned that most of their children had never been to a party where the main activity was not getting high. The parents’ solution: workshops showing kids how to give successful drug-and-alcohol-free parties. Says Margery Ranch, PWC director, " We’ve seen a change in attitude. Young people are feeling more comfortable saying no.

The main idea of Paragraph 1 is that()

A. society pays little attention to drug use among teenagers

B. drug-abuse has become a common problem among teenagers

C. parents are angry at children’s drug-abuse

D. children use alcohol more often than drug