(a) Explain the term resonance and give two examples

(b)(i) Describe, with the aid of a labelled diagram, an experiment to show how the frequency of the note emitted by a vibrating string depends on the length of the string.

(ii) State two precautions necessary to obtain an accurate result.

(c) A sonometer wire is plucked and it vibrates emitting a fundamental note. State the effect on the frequency of the note if the

(i) tension in the wire were made nine times as large with no change in the length of the wire;

(ii) length of the wire were doubled with no change in the tension.

(a) Sketch the form of the magnetic flux pattern due to a current flowing

(i) in a long solenoid

(ii) through two long straight parallel wires when the directions of the current are opposite. (Neglect the earth's magnetic field).

(b) Draw a labelled diagram of an electric bell and explain how it works

(c) An electric bell takes a current of 0.2A groin a battery of two dry cells connected in series. Each cell has an e.m.f. of 1.5V and an internal resistance of 1.0\(\Omega\).

(i) Calculate the effective resistance of the bell

(ii) What current would the bells take in the cells were arranged in parallel?

(a) Briefly explain what would happen to a stable element if it is bombarded by \(\alpha\)-particles

(b) Explain how the bombardment of Uranium with neutrons could lead to nuclear fission chain reaction and hence nuclear explosion.

(c) State three characteristics of nuclear activity

(d) State three applications of atomic energy

(e) State two postulates of Bohr's model of the atom and two limitations of such a model

(a) Explain with the aid of a diagram what is meant by the moment of a force about a point.

(b) State the conditions of equilibrium for a number of coplanar parallel forces. 

A metre rule is found to balance at the 48cm mark. When a body of mass 60g is suspended at the 6cm mark, the balance point is found to be at the 30cm mark. Calculate:

(i) the mass of the metre rule; (ii) the distance of the balance point from the zero end, if the body were moved to the 13cm mark.

(c) Show that the efficiency E, the force ratio M.A and the velocity ratio V.R of a machine are related by the equation \(E = \frac{M.A}{V.R} \times 100%\)

The efficiency of a machine is 80%. Determine the work done by a person using this machine to raise a load of 200kg through a vertical distance of 3.0m.

[Take g = 10ms\(^{-2}\)]

(a) Draw a labelled diagram of a vacuum flask. Explain how its construction minimizes heat exchange with the surroundings.

(b) State Boyle's law. A thread of mercury of length 15cm is used to trap some air in a capillary tube with uniform cross- sectional area and closed at one end with the tube vertical and the open end uppermost, the length of the trapped air column is 20cm. Calculate the length of the air column when the tube is held:

(i) Horizontally ; (ii) vertically with the open end underneath. [Atmospheric pressure = 76cm Hg]

(c) Explain why it is not advisable to sterilize a clinical thermometer in boiling water at normal atmospheric pressure.