2
PAPER 2
\( 11 / 2 \) hours
EssAY
[60 marks]
Answer eight questions in all; five questions from Part I and three questions from Part II.
PART I
[15 marks]
Answer any five questions from this part.
All questions carry equal marks.
1. The frequency, \( f \), of a wave in a string is given in terms of length, \( L \), of the string, the tension, \( T \), in the string and the linear density, \( \rho \), by the formula,
\[
f=\frac{1}{2 L} \sqrt{\frac{T}{\rho}}
\]
Obtain the basic units of \( f \) using dimensional analysis.
[3 marks]
2. A satellite orbits the earth in a path of radius, \( R \).
(a) Name the two forces that act on the satellite.
(b) Show that the velocity, \( v \), of the satellite is related to \( R \) by the expression
\[
v \propto \frac{1}{\sqrt{R}} \text {. }
\]
3. A force of \( 50 \mathrm{pN} \) is required to stretch a sample of DNA strand of length \( 50 \mathrm{~nm} \) by \( 10 \% \) of its original length. Determine the cross-sectional area of the DNA strand.
\[
\text { [Young's Modulus, } \mathrm{E}=1.0 \times 10^{8} \mathrm{~N} \mathrm{~m}^{-2} \text { ] }
\]
[3 marks]
4. (a) A ball projected vertically upwards reached a maximum height of \( 35.0 \mathrm{~m} \) before returning to the level of projection. Calculate the velocity of projection.
\[
\left[\mathrm{g}=10 \mathrm{~m} \mathrm{~s}^{-2}\right]
\]
(b) State two factors that affect projectile motions.
[3 marks]
5. The following elements were compared at low temperatures. Copy and complete the table.
\begin{tabular}{|c|l|l|l|}
\hline & Insulators & Semiconductors & Metals \\
\hline \begin{tabular}{c}
Location of \\
eloctrons
\end{tabular} & & & \\
\hline \begin{tabular}{c}
Width of \\
forbidden gap
\end{tabular} & & & \\
\hline
\end{tabular}
6. (a) State two applications of optical fibres.
[3 marks]
(b) Explain why the core of an optical fibre is made very thin.
7. State three applications of ferromagnetic materials.
[3 marks]
[3 marks]
