3.9 计量单位转换
章节大纲
-
How can a number of track laps be converted to a distance in meters?
::如何将多条轨道圈转换成距离(米)?You are training for a 10-kilometer run by doing laps on a 400-meter track. You ask yourself “How many times do I need to run around this track in order to cover ten kilometers?” (more than you realize). By using , you can easily determine the number of laps needed to cover the 10 k distance.
::您正在训练如何在400米长的轨道上行走10公里长的车程。 您问自己 : “ 为了覆盖10公里长,我需要绕道跑多少次? ” ( 比你所意识到的还要多 ) 。 通过使用 , 您可以很容易地确定要覆盖10公里长的车程需要多少长的车程 。Metric Unit Conversions
::计量单位转换The metric system’s many prefixes allow quantities to be expressed in many different units. Dimensional analysis is useful to convert from one metric system unit to another.
::衡量系统的许多前缀允许用许多不同单位表示数量。 度量分析有助于将一个计量系统单位转换为另一个单位。Sample Problem: Metric Unit Conversions
::问题:计量单位转换A particular requires 120 mL of a solution. The teacher knows that he will need to make enough solution for 40 experiments to be performed throughout the day. How many liters of solution should he prepare?
::特殊需要120毫升的解决方案。 教师知道,他需要为全天进行40次实验做出足够的解决方案。 他应该准备多少升的解决方案?Step 1: List the known quantities and plan the problem.
::第1步:列出已知数量并规划问题。Known
::已知已知-
1 exp requires 120 mL
::1 表示需要120毫升 -
1 L = 1000 mL
::1升=1000毫升
Unknown
::未知-
L of solution for 40 exp
::40分钟的L解决办法
Since each experiment requires 120 ml of solution and the teacher needs to prepare enough for 40 experiments, multiply 120 by 40 to get 4800 mL of solution needed. Now you must convert ml to L by using a conversion factor .
::由于每次实验需要120毫升的溶液,教师需要为40次实验做好准备,120乘以40,以获得4800毫升的溶液。现在,你必须使用转换系数将毫升转换为L。Step 2: Calculate
::第2步:计算
::8800毫升1 L1000毫升=4.8升Note that conversion factor is arranged so that the mL unit is in the denominator and thus cancels out, leaving L as the remaining unit in the answer.
::请注意,换算系数的安排是使毫升单位在分母中,从而取消,在回答中将L作为剩余单位。Step 3: Think about your result.
::步骤3:想想你的结果。A liter is much larger than a milliliter, so it makes sense that the number of liters required is less than the number of milliliters.
::一升比一毫升要大得多,因此,要求的升数比毫升少是有道理的。Two-Step Metric Unit Conversions
::二级二级计量单位转换Some metric conversion problems are most easily solved by breaking them down into more than one step. When both the given unit and the desired unit have prefixes, one can first convert to the simple (unprefixed) unit, followed by a conversion to the desired unit. An example will illustrate this method.
::一些计量转换问题最容易通过将其分解为不止一步来解决。当给定单位和所需单位都有前缀时,可以首先转换为简单(未加固定)单位,然后转换为所需单位。举例将说明这一方法。Sample Problem: Two-Step Metric Conversion
::抽样问题:两步制转换Convert 4.3 cm to μm.
::将4.3厘米转换为微米。Step 1: List the known quantities and plan the problem.
::第1步:列出已知数量并规划问题。Known
::已知已知-
1 m = 100 cm
::1米=100厘米 -
1 m = 10
6
μm
::1米=106微米
Unknown
::未知-
4.3 cm = ? μm
::4.3厘米=? 微米
You may need to consult a table for the multiplication factor represented by each metric prefix. First convert cm to m, followed by a conversion of m to μm.
::您可能需要查看一个表格,显示每个公吨前缀代表的乘数系数。 第一次转换 cm m, 之后将 m 转换为 μm 。Step 2: Calculate
::第2步:计算
::4.3厘米×1米100厘米×106 微米1 m= 43 000 微米Each conversion factor is written so that unit of the denominator cancels with the unit of the numerator of the previous factor.
::每个换算系数都写成,使分母的单位与前一个系数的分子单位注销。Step 3: Think about your result.
::步骤3:想想你的结果。A micrometer is a smaller unit of length than a centimeter, so the answer in micrometers is larger than the number of centimeters given.
::微米的长度小于一厘米,因此微米的答案大于给出的厘米数。Summary
::摘要-
Dimensional analysis can be used to carry out metric unit conversions.
::度量分析可用于进行计量单位转换。
Review
::回顾-
Perform the following conversions.
-
0.074 km to m
::0.074公里至米 -
24,600 μg to g
::24,600微克至克 -
4.9 × 10
7
μg to kg
::4.9 × 107 微克至千克 -
84 dm to mm
::84 dm至毫米
::执行以下转换: 0.074公里到m 24 600 微克到g 4.9 × 107 微克到千克 84 dm 到 毫米 -
0.074 km to m
-
1 exp requires 120 mL
