Evan's Space

Wonders of Physics


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Density (Units Conversion) and Floatation

Density is the mass per unit volume.

Common units for density are g/cm3 or kg/m3. SI unit is kg/m3.

Density of a pure substance is fixed, regardless of it’s size!

density

Floating and Sinking

A denser (heavier) substance will sink in liquid which is less denser (lighter).
A less dense substance will float in a liquid which is denser.
If substance has the same density as the liquid, it will be suspended in the liquid.

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Conversion of m/s to km/h and vice versa – Usain Bolt’s world record for 100m

Usain Bolt smashed the 100m and 200m World record with a time of 9.58 s and 19.19s respectively in Berlin 2009! Can’t embed the 100m clip here. So just how fast is he? Is he much faster than your dad’s car on the expressway 90 km/h???

100m in 9.58s means approx. 10.44 m/s = 37.58 km/h. So well, 2 legs are slower than 4 wheels =) How do you convert?  

View the step by step conversion from m/s to km/h. (in short, multiply by 3.6) 

Below is another record set by him. 200m in 19.19s. You can try to do the conversion!