In Physics, scientific notations are useful when it comes to approximation (approx.). Why? Because it gives the meaningful nor real result (s).

Isn't the answer to the example 2.1x10² after adding the two exponent ie -3 an ď 4?

The right answer to the last example is \( 1.024×10^{-17} \).
Because the power is \( -38-(-21)=17 \), and not \( -38-(-19)=18 \)
The incorrect thing was in the last power

Hard works put in simple words,still hard for me

<h2>Scientific Notation</h2>
<p>In science one often needs to work with very large or very small numbers. These can be written more easily (and more compactly) in scientific notation, in the general form:</p>
<h4>\(N × 10^n\)</h4>
<p class="para">where \(N\) is a decimal number between 0 and 10 that is rounded off to a few decimal places. \(n\) is known as the <i class="emphasis">exponent</i> and is an integer. If \(n &gt; 0\), it represents how many times the decimal place in \(N\) should be moved to the right. If \(n &lt; 0\), then it represents how many times the decimal place in \(N\) should be moved to the left. For example 3.24 × 10<sup class="sup">3</sup> represents 3240 (the decimal moved three places to the right) and 3.24 × 10<sup class="sup">−3</sup> represents 0.003 24 (the decimal moved three places to the left).</p>
<p class="para">If a number must be converted into scientific notation, we need to work out how many times the number must be multiplied or divided by 10 to make it into a number between 1 and 10 (i.e. the value of \(n\)) and what this number between 1 and 10 is (the value of \(N\)). We do this by counting the number of decimal places the decimal comma must move.</p>
<p class="para">For example, write the speed of light (299,792,458 ms<sup class="sup">−1</sup>) in scientific notation, to two decimal places. First, we find where the decimal comma must go for two decimal places (to find \(N\)) and then count how many places there are after the decimal comma to determine \(n\).</p>
<p class="para">In this example, the decimal comma must go after the first 2, but since the number after the 9 is 7, \(N = 3.00\). \(n = 8\) because there are 8 digits left after the decimal comma. So the speed of light in scientific notation, to two decimal places is 3.00 × 10<sup class="sup">8</sup> ms<sup class="sup">−1</sup>.</p>
<p class="para">We can also perform addition, subtraction, multiplication and division with scientific notation. The following two worked examples show how to do this:</p>
<div class="ns-school-emp">
<h3 class="example-header"><span class="cnx_label">Example 1: </span><strong class="title">Addition and Subtraction with Scientific Notation</strong></h3>
<div class="ns-school-defn">
<h4><strong>Question</strong></h4>
<p>\(1.99 × 10^{-26} + 1.67 × 10^{-27} \; - \; 2.79 × 10^{-25}\)</p>
<h4 class="section-header"><strong class="title">Answer</strong></h4>
<div class="section"><strong class="title">Make all the exponents the same</strong>
<p class="para">To add or subtract numbers in scientific notation we must make all the exponents the same:</p>
<p class="para">1.99 × 10<sup class="sup">−26</sup> <span style="white-space: nowrap;">= </span>0.199 × 10<sup class="sup">−25</sup> and</p>
<p class="para">1.67 × 10<sup class="sup">−27</sup> <span style="white-space: nowrap;">= </span>0.0167 × 10<sup class="sup">−25</sup></p>
</div>
<div class="section"><strong class="title">Carry out the addition and subtraction</strong></div>
<p>Now that the exponents are the same we can simply add or subtract the \(N\) part of each number:</p>
<h4>\(0.199 + 0.0167 \; - \; 2.79 = -2.5743\)</h4>
<strong class="title">Write the final answer</strong>
<p class="para">To get the final answer we put the common exponent back:</p>
<p class="para">\(−2,5743 × 10^{-25}\)</p>
</div>
</div>
<p>Note that we follow the same process if the exponents are positive. For example \(5.1 × 10^3 + 4.2 × 10^4 = 4.71 × 10^4.\)</p>
<div class="ns-school-emp">
<h3 class="example-header"><span class="cnx_label">Example 2: </span><strong class="title">Multiplication and Division with Scientific Notation</strong></h3>
<div class="ns-school-defn">
<h4><strong>Question</strong></h4>
<p>\(1.6 × 10^{-19} × 3.2 × 10^{-19} ÷ 5 × 10^{-21}\)</p>
<h4 class="section-header"><strong class="title">Answer</strong></h4>
<div class="section"><strong class="title">Carry out the multiplication</strong>
<p class="para">For multiplication and division the exponents do not need to be the same. For multiplication we add the exponents and multiply the \(N\) terms:</p>
<p>\(1.6 × 10^{-19} × 3.2 × 10^{-19} = (1.6 × 3.2) × 10^{-19 + (-19)} = 5.12 × 10^{-38}\)</p>
</div>
<div class="section"><strong class="title">Carry out the division</strong>
<p class="para">For division we subtract the exponents and divide the \(N\) terms. Using our result from the previous step we get:</p>
<p>\(2.56 × 10^{-38} ÷ 5 × 10^{-21} = (5.12 ÷ 5) × 10^{-38 - (-19)} = 1.024 × 10^{-18}\)</p>
</div>
<strong class="title">Write the final answer</strong>
<p class="para">The answer is: \(1.024 × 10^{-18}\)</p>
</div>
</div>
<p>Note that we follow the same process if the exponents are positive. For example: \(5.1 × 10^{-3} × 4.2 × 10^4 = 21.42 × 10^7 = 2.142 × 10^8\)</p>

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Scientific Notation

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Explore various scientific concepts and practical skills, including scientific notation, unit conversions, rates, ratios, constants, and the scientific method, as well as laboratory safety procedures and designing models.


Scientific Notation

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