Two wires $\mathrm{P}$ and $\mathrm{Q}$ both obey Hooke's law. They are both stretched and have the same strain. The Young modulus of $\mathrm{P}$ is four times larger than that of $\mathrm{Q}$. The diameter of $\mathrm{P}$ is twice that of $\mathrm{Q}$. What is the ratio of the tension in $\mathrm{P}$ to the tension in $\mathrm{Q}$ ?

(A) $\frac{1}{2}$

(B) $1$0

(C) $2$

(D) $16$

Define density.

State the SI base units in which density is measured.

(b (i) Define pressure.

State the SI base units in which pressure is measured.

A sample of fishing line is $1.0 \mathrm{m}$ long and is of circular cross-section of radius $0.25 \mathrm{mm}$. When a weight is hung on the line, the extension is $50 \mathrm{mm}$ and the stress is $2.0\times {10}^8 \mathrm{Pa}$. Calculate the cross-sectional area of the line.

A sample of fishing line is $1.0 \mathrm{m}$ long and is of circular cross-section of radius $0.25 \mathrm{mm}$. When a weight is hung on the line, the extension is $50 \mathrm{mm}$ and the stress is $2.0\times {10}^8 \mathrm{Pa}$. Calculate the young modulus.