**THE UNITED REPUBLIC OF TANZANIA ****NATIONAL EXAMINATIONS COUNCIL OF TANZANIA**

**ADVANCED CERTIFICATE OF SECONDARY EDUCATION ****EXAMINATIONS**

**131/1 PHYSICS 1**

(For Both School and Private Candidates)

*Time: 3 Hours Year: 2023*

**Instructions**

- This paper consists of sections A and B with a total of ten (10) questions.
- Answer all questions in section A and choose two (2) questions from section B.
- Marks for each question or part thereof are indicated.
- Mathematical tables and non-programmable calculators may be used.
- All writing must be in blue or black ink except drawing which must be in pencil.
- Cellular phones and any other unauthorized materials are not allowed in the examination room.
- Write your Examination Number on every page of your answer booklet(s).
- The following information may be useful:

- Acceleration due to gravity, g = 9.8 m/s
^{2} - The ratio of specific heat capacity, γ = 1.4
- 1 g of water = 1 cm
^{3} - Latent heat of vaporization of water = 2256 Jg
^{-1} - Density of water = 10
^{3} kg/m^{3} - Pie, π = 3.14.

**SECTION A (70 Marks)**

Answer **all** questions from this section.

1. (a) (i) How is the term dimension differ from dimensional formula? **(02 marks)**

(ii) Apply the method of dimension to deduce the value of *x* in the expression F = kAρV^{X} , where F, V, A, ρ and k are the force acting on the body, speed, surface area, density and dimensionless constant respectively. **(04 marks)**

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(b) The pressure P can be calculated from the relation, where F is the force and R the radius. If the percentage errors of F and R are ± 2 and ± 1 respectively, determine the possible percentage error of **P.** **(04 marks)**

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2. (a) How is the horizontal range of a projectile affected when its initial velocity is doubled for a given angle of projection, θ ? **(04 marks)**

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(b) An aircraft travelling at 150 km/hr dropped a luggage of food to flood victims isolated on a patch of land 250 m below. Determine:

(i) The time on which the luggage should be dropped before the aircraft is directed overhead. **(03 marks)**

(ii) The speed of luggage as it reaches the ground. **(03 marks)**

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3. (a) A car is moving with a speed of 40 m/s around unbanked curve of radius 500 m. Determine the least coefficient of friction which allows the car to negotiate the curve without sliding. **(03 marks)**

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(b) A stone of mass 1 kg attached to a string of length I m is whirled in a horizontal circle of radius 0.6 m at a constant speed. Calculate;

(i) The tension in the string. **(04 marks)**

(ii) The maximum number of revolutions per second it can make. **(03 marks)**

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4. (a) (i) Give two daily life examples on which Newton's first law of motion applies. **(02 marks)**

(ii) Sand drops vertically at the rate of 100 g/s on a horizontal conveyor belt moving at, a steady velocity of 5 cm/s. Find the force required to keep the belt moving. **(03 marks)**

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(b) *Figure 1 *shows the system of forces being at equilibrium.

Determine the maximum value of the force Q if the friction force on the block cannot exceed 12 N. **(05 marks)**

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5. (a) A motor car Tyre has a pressure of 4 atmospheres at a room temperature of 27^{o}C. If the Tyre suddenly burst, calculate the temperature of the escaping air. **(03 marks)**

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(b) (i) Distinguish between triple point of water and thermometric property as used in heat. **(03 marks)**

(ii) The resistance R_{θ} of a particular resistance thermometer at a Celsius temperature θ as measured by a constant volume gas thermometer is given as R_{θ} = 2.50 x 10 ^{-}^{4} θ^{2} + 0.1850θ +40.0 . Calculate the temperature as measured on the scale of the resistance thermometer which corresponds to a temperature of 70^{o }C on the gas thermometer. **(04 marks)**

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6. (a) (i) What is meant by reversible process as applied in thermodynamics? **(01 mark)**

(ii) Distinguish isobaric process from isochoric process. **(03 marks)**

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(b) If 1 g of water is subjected at a pressure of 1.013 x 10^{5} Pa it becomes 1671 cm^{3} of steam. Calculate;

(i) The external work done. **(03 marks)**

(ii) The increase in internal energy of the system. **(03 marks)**

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7. (a) Analyse three possible solutions to the side effects of global warming. **(03 marks)**

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(b) (i) Briefly explain four major causes of water pollution. **(04 marks)**

(ii) What are the three disadvantages of using solar energy? **(03 marks)**

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**SECTION B (30 Marks)**

Answer **two (2)** questions from this section.

8. (a) (i) Identify two conservation laws embodied in Kirchhoffs rules stating its physical significance.** (02 marks) **

(ii) Why is it safe for a bird to stand on a high voltage wire without being harmed? **(02 marks)**

(b) Study the circuit diagram in Figure 2 and apply KirchhofPs rules to find the values of the currents 11 , 12 and 13. **(04 marks)**

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(c) (i) A capacitor of 1 'IF is used in a television circuit where the frequency and the current flowing are 1000 Hz and 2 mA (r.m.s) respectively. Compute the voltage across the capacitor. **(03 marks)**

(ii) Determine the current flowing when an a.c voltage of 20 V (r.m.s) and frequency of 50 Hz is connected to a capacitor in 8 (c) (i). **(04 marks)**

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9. (a) (i) Comment on the argument that electrical conductivity of a semiconductor depends on temperature variation. **(02 marks)**

(ii) Draw a circuit diagram showing a reverse biased diode. **(0? marks)**

(iii) Why there is a very little current flow in the circuit drawn in (a) (ii)? **(01 mark) **

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(b) (i) Study the circuit diagram in Figure 3 then find the gain of the amplifier.

**(03 marks)**

(ii) Generate the truth table for the logic gates in Figure 4. **(03 marks)**

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(c) (i) What is meant by a voltage follower? Give one importance. **(02 marks) **

(ii) Draw a diagram to show an Op-Amp as a voltage follower. **(02 marks)**

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10. (a) (i) Sketch the circuit symbol for **NPN** transistor showing the direction of a convectional current. **(02 marks)**

(ii) Under what condition does a semiconductor diode behave as an open switch? **(02 marks)**

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(b) (i) Why insulators do not conduct electricity under ordinary condition? Explain in terms of energy band theory. **(03 marks)**

(ii) A common emitter amplifier has an input resistance of 0.5 Q and output resistance of 45 Q. If the current gain, β = 65; find the voltage gain. **(03 marks)**

(c) (i) What is the purpose of the barrier potential difference in a P-N Junction? **(02 marks) **

(ii) Identify two advantages of a junction diode and sketch its characteristic curve which shows how it can act as a rectifier. **(03 marks)**

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