Question

Q1. The density of air at room temperature is about 1.2 g/cm^3. this is the same as a) 12 kg/m^3b) 120 kg/m^3c) 1200 kg/m^3 Q2. a rock suspended by a weighing scale weighs 3 N when submerged in H20 & 5 N out of H20. what is the buoyant force of the rock?a) 8 Nb) 5 Nc) 3 N d) 2 N

Answer 1

In order to convert from g/cm^3 to kg/m^3, we can convert separately each unit:

1 g = 10^-3 kg

1 cm^3 = (10^-2)^3 m^3 = 10^-6 m^3

So we can convert doing the following steps:

$1.2\frac{g}{\operatorname{cm}^3}=1.2\frac{10^{-3}kg}{10^{-6}m^3}=1.2\cdot\frac{10^{-3}}{10^{-6}}\frac{kg}{m^3}=1.2\cdot10^3^{}\frac{kg}{m^3}=1200\frac{kg}{m^3}$

Therefore the correct option is C.