ZANZIBAR PRIVATES SCHOOLS

FORM SIX JOINTS EXAMINATIONS

131/2 PHYSICS 2

Time: 3 Hours Thursday, 21st March 2024 a.m.

Instructions:
1. This paper consists of six (6) questions. Answer any five (5) questions.
2. Each question carries twenty (20) marks.
3. Use a blue or black pen in writing. The diagrams must be in a pencil.
4. Mobile phones and any unauthorized materials are prohibited in the examination room.
5. Mathematical tables and non-programmable calculators may be used.
6. Write your Examination Number on every page of your answer booklet(s).
7. The following constants may be useful
(a) Acceleration due to gravity g  9.8m / s 2
(b) Density of water 𝑔
(c) Permeability of free space
(d) The permittivity of free space
(e) Speed of sound of light,
(f) Atmospheric pressure
(g) Young’s modulus of copper
(h) Young’s modulus of steel
(i) Young’s modulus of rubber
(j) The surface tension of soap solution
(k) Mass of electron, 𝑔
(l) Plank’s constant, 𝑕
(m) 1 year = 364 days
(n) Avogadro’s number,

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1. (a)(i) State the principle on which Bernoulli’s theorem is based. (02 marks)
(ii) Why does the speed of a liquid increases and its pressure decreases when a liquid pass
through constriction in a pipe? (03 marks)

(b) (i) Why is parachute used while jumping from an aero plane? (02 marks)
(ii) Water flow steady through a horizontal pipe which consists of two parts joining end
to end one is 21 long and has a diameter of 0.225 and the other is 7 long
with a diameter of 0.075 cm. If the pressure across the two extremes end of
combination is 14 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟. Find the pressure difference between ends of each
parts (05 marks)

(c) (i) Explain why machine parts are jammed during winter? (02 marks)
(ii) A cylindrical tank with large diameter is filled with water to a depth 0.3 m. A hole of
cross-sectional area of 6.5 cm2 in the bottom of the tank allows water to drain out,
what is the drainage rate? At what distance below the bottom of the tank is the cross-
sectional area of the steam equal to one half the area of the hole? (Rate should be in
m3/s) (06 marks)

2. (a) (i) What is standing wave? (02 marks)

(ii) Explain how standing waves are formed in a string. (03 marks)
(b) State three (3) factors affecting the frequency of the vibrating string in a sonometer.
(03 marks)
(c) A string was stretched to a fundamental frequency of 220 Hz. Its length changed until it
vibrates at 440 Hz without changing the tension. Its length changed again so that it now
vibrates in unison with a wire of unknown frequency. If the two lengths are 90 cm and
70.7 cm respectively. Determine:
(i) The original length of the wire (04 marks)
(ii) The unknown frequency (03 marks)

(d) Light of wavelength 4500 passes through a single slit of width 0.015 m. Find the
angular deflection to the first dark band of the diffraction pattern. (05 marks)

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3. (a) Briefly explain the following observation
(i) Soap solution is better cleaning agent than ordinary water (02 marks)
(ii) Hot soup is tastier than the cold soup (02 marks)

(b) What amount of energy will be liberated if 1000 𝑑𝑟𝑜𝑝𝑙𝑒𝑡 of water each 10-8 diameter
coalesce to form large spherical drop? (04 marks)

(c) (i) What will happen to a material if elastic limit is exceeded (02 marks)
(ii) Two exactly similar wire of steel and copper are stretched by equal forces. If the total

elongation is 1 find how much each wire is elongated. (04 marks)

(d) From figure 1, a rod MP consist of three segment MN, NO and OP is hanging vertically
from a fixed point M. The length of the segment are respectively 0.15m, 0.1m and 0.2m.
The cross section of the rod is uniformly 10-4m2. A weight of 20 kg is hang from P.
Calculate the displacement of point N, O and P. Neglect the weight of the rod. Given
YMN = 2.5×1010N/m2, YNO = 4×1010N/m2, YOP = 1010N/m2

Figure 1

Hint!! Figure 1 shows the condition of the problem. Here MNOP is the initial position
of the rod. When a weight is applied at the end P the rod (06 marks)

4. (a) Define the term electric potential at a point in an electric field. (02 marks)
(b) An electric field is established between two parallel plates as shown in the figure
below. The plates are 50cm apart and a p.d of 1000 V is applied between them. A
point change of value +1 x 10-6 C is held at point A. It is moved first to B then to C
and finally back to A. The distances are shown in the diagram below

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 B

Figure 2

Calculate
(i) The force experienced by the charge at A and at B (02 marks)
(ii) The energy involved in moving the charge from A to B (02 marks)
(iii) The energy required to move the charge from C to A (02 marks)
(iv) The net energy needed to move the charge along the route ABCA (02 marks)

(c) A 4 x10-6F capacitor is charged by 120 V supply and is then discharged through 15
x 105 Ω resistor.
(i) Obtain the time constant (02 marks)
(ii) Calculate the charge on the capacitor at the start of the discharge (02 marks)
(iii) What will be the value of the charge on the capacitor, the potential difference

across the capacitor and the current in the circuit 5 seconds after the discharge
starts? (06 marks)

5. (a) Draw the diagram of the solenoid with certain number of turns placed in the
magnetic field and indicate a suitable direction of the flow of current in it.
(03 marks)
(b) Consider two parallel co-axial circular coils of equal radius R, and number of turns
N, carrying equal currents I in the same direction and separated by a distance R.
Show that where B is the field on the axis around the mid-point

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 between the coils which is uniformly distributed over a distance that is small as
compared to R and is the permeability of free space. (04 marks)

(c) A current of 1.0 A flows in a 1.0m length of copper wire of cross sectional area
1.0mm2.
28
(i) Given that each cubic metre of copper contains 9 x 10 conduction electrons
each of charge = 1.6 x 10-19 C calculate the average drift velocity of the
electrons. (3 marks)
-2
(ii) If the wire is placed at right angles to a magnetic field of 1.0 x 10 T. Calculate

the average force experienced by each electron due to the field (03 marks)
(iii) What is the total force experienced by the wire due to the field (02 marks)

(d) An electron is accelerated from rest by a potential difference of 350 V, it then

enters a uniform magnetic field of magnitude 200 10-3 T with its velocity
perpendicular to the field. Calculate the speed of the electron and the radius of its
path in the magnetic field. (05 marks)

6. (a) (i) Why a single nucleus cannot emit -particle, -particle and -rays together?
(02 marks)
(ii) Briefly explain the significance of Binding energy per nucleon. (02 marks)

(b) As X-ray unit operating at 100 kV produces a current of 20 mA. Use this
information to calculate
(i) The number of electrons striking the target per second. (02 marks)
(ii) The speed of the electron incident on the target (02 marks)
(iii) The lowest wavelength of the continuous x-ray spectra. (02 marks)

(c) (i) Use Bohr’s model to determine the ionisation energy of the He+ ion. (03 marks)
(ii) Calculate the minimum wavelength a photon in (c) (i) above must have to cause

ionisation. (03 marks)

(d) The half-life of against alpha decay is 4.5 × 104 years. How much
disintegration per second occur in 1g of (04 marks)

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