IB myp 4-5 physics – Practice Questions- All Topics
Topic :Forces and energy-Density
Topic :Forces and energy– Weightage : 21 %
All Questions for Topic :States & properties of matter, kinetic particle theory, density, pressure, molecular arrangements
Question
The density of air is about $1.2 \mathrm{~kg} \mathrm{~m}^{-3}$. Estimate the mass of air in the room that you are in.
▶️Answer/Explanation
For example: Let volume of room $=100 \mathrm{~m}^3$; $m=1.2 \times 100=120 \mathrm{~kg}$
Question
Iron has a density of $7,870 \mathrm{~kg} \mathrm{~m}^{-3}$. Calculate the volume of iron which would have the same mass as your answer above.
▶️Answer/Explanation
$\frac{120}{7,870}=0.0152 \mathrm{~m}^3$
Question
The kilogram is defined by a cylinder of platinum iridium alloy called the international prototype kilogram kept in Paris. The cylinder has a density of $21,186 \mathrm{~kg} \mathrm{~m}^{-3}$ and a height of $39.17 \mathrm{~mm}$.
a) Calculate the cross-sectional area of the cylinder.
b) Calculate the diameter of the cylinder.
▶️Answer/Explanation
a)
$
\begin{aligned}
& V=\frac{1}{21,186}=4.72 \times 10^{-5} \mathrm{~m}^3 \\
& A=\frac{4.72 \times 10^{-5}}{0.03917}=1.21 \times 10^{-3} \mathrm{~m}^2
\end{aligned}
$
b) $2 \sqrt{\frac{0.00121}{\pi}}=0.0392 \mathrm{~m}$