Question

4. Express each of the following speeds in metre per seconds
72 km per hour ​

Answer 1

Answer:

$Express the 72 \dfrac{km}{hr} </p><p>hr</p><p>km</p><p> </p><p> is 20 \dfrac{m}{sec} </p><p>sec</p><p>m</p><p> </p><p> .</p><p>Step-by-step explanation:</p><p></p><p>We have,</p><p></p><p>72 \dfrac{km}{hr} </p><p>hr</p><p>km</p><p> </p><p> </p><p></p><p>To express the speed in meter per second = ?</p><p></p><p>We know that,</p><p></p><p>1 km = 1000 m and</p><p></p><p>1 hr = 3600 sec</p><p></p><p>∴ 72 \dfrac{km}{hr} </p><p>hr</p><p>km</p><p> </p><p> </p><p></p><p>= 72 \dfrac{1000m}{3600sec} </p><p>3600sec</p><p>1000m</p><p> </p><p> </p><p></p><p>= 72\times \dfrac{1000}{3600}\dfrac{m}{sec}=72× </p><p>3600</p><p>1000</p><p> </p><p> </p><p>sec</p><p>m</p><p> </p><p> </p><p></p><p>=72\times \dfrac{10}{36}\dfrac{m}{sec}=72× </p><p>36</p><p>10</p><p> </p><p> </p><p>sec</p><p>m</p><p> </p><p> </p><p></p><p>=2\times 10\dfrac{m}{sec}=2×10 </p><p>sec</p><p>m</p><p> </p><p> </p><p></p><p>= 20 \dfrac{m}{sec} </p><p>sec</p><p>m</p><p> </p><p> </p><p></p><p>Trick:</p><p></p><p>Convert \dfrac{km}{hr} </p><p>hr</p><p>km</p><p> </p><p> to \dfrac{m}{sec} </p><p>sec</p><p>m</p><p> </p><p> </p><p></p><p>Multiply by \dfrac{5}{18} </p><p>18</p><p>5</p><p> </p><p> </p><p></p><p>72 \dfrac{km}{hr} </p><p>hr</p><p>km</p><p> </p><p> </p><p></p><p>= 72 × \dfrac{5}{18} </p><p>18</p><p>5</p><p> </p><p> \dfrac{m}{sec} </p><p>sec</p><p>m</p><p> </p><p> </p><p></p><p>= 4 × 5 = 20 \dfrac{m}{sec} </p><p>sec</p><p>m</p><p> </p><p> </p><p></p><p>Hence, to express the 72 \dfrac{km}{hr} </p><p>hr</p><p>km</p><p> </p><p> is 20 \dfrac{m}{sec} </p><p>sec</p><p>m</p><p> </p><p> .$

Step-by-step explanation:

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Answer 2

Answer:

1st method:

72 km/h =( 72 × 1000) / 60 × 60

= 72000/3600

= 20 m/s

2nd method:

72 km/h = 72 × 5/18

= 4×5

= 20 m/s

Step-by-step explanation:

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