131/1 PHYSICS 1

(For Both School and Private Candidates)

Time 3 Hours Year: 2014


1. This paper consists of sections A and B with a total of ten (10) questions.

 2. Answer all questions in section A and two (2) questions from section B. 

3. Section A carries seventy (70) marks and Section B carries thirty (30) marks. 

4. Marks for each question or part thereof are indicated. 

5. Mathematical tables and non-programmable calculators may be used. 

6. Cellular phones and any unauthorized materials are not allowed in the examination room. 

7. Write your Examination Number on every page of your answer booklet(s). 

8. The following information may be useful: 

Thermal conductivity of copper = 400Wm 11<-1

Acceleration due to gravity g -10m/s2

Stefan's constantimage

Exponential constant e = 2.7

Electronic charge e = 1.6 x 10-19C

Temperature coefficient of resistance for nichrome = 8.0 x 10 51C1

Resistivity of nichrome at 373K = 1.08 x 10 6QM

1.  (a) (i) Distinguish random error from systematic error.

(ii) Give a practical example of each term in 1 (a) (i) and briefly explain how they can be reduced or eliminated.

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(b) (i) Define the terms error and mistake.

(ii) An experiment was done to find the acceleration due to gravity by using the formula: 

where all symbols carry their usual meaning.

If the clock loses 3 seconds in 5 minutes, determine the error in measuring 'g', given that, T=2.22sec, 121.6cm, ATI =0.1sec and Al=+-0.05

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(c) (i) What is the importance of dimensional analysis in spite of its drawbacks?

(ii) The following measurements were taken by a student for the length of a piece of rod: 21.02, 20.99, 20.92, 21.11 and 20.69. Basing on error analysis find the true value of the length of the piece of rod and its  associated error.

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2. (a) Outline the motions that add up to make projectile motion.

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 (b)      In the first second of its flight a rocket ejects —60 of its mass with a relative velocity of 2400m/s.

(i)      Find its acceleration.

(ii)   What is the final velocity if the ratio of initial to final mass of the rocket is 4 at a time of 60 seconds?

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(c)      A ball is thrown upwards with an initial velocity of 33m/s from a point 65 0 on the side of a hill which slopes upward uniformly at an angle of 28 0 .

(i)      At what distance up the slope does the ball strike?

(ii)   Calculate the time of the flight of the ball.

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3. (a) (i) State the principle of conservation of linear momentum. 

(ii) Give two examples of the principle stated in 3(a) (i).

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(b) A cannon of mass 1300kg fires a 72kg ball in a horizontal direction with a nuzzle speed of 55m/s. If the cannon is mounted so that it can recoil freely calculate the:

(i)       Recoil velocity of the cannon relative to the earth.

(ii)      Horizontal velocity of the ball relative to the earth.

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(c) (i) Define the term 'radial acceleration'.

(ii) An insect is released from rest at the top of the smooth bowling ball such that it slides over the ball. Prove that it will lose its footing with the ball at an angle of about 48 0 with the vertical.

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4. (a) (i) State where the magnitude of acceleration is greatest in a simple harmonic motion (S.

(ii) Sketch a graph of acceleration against displacement for a simple harmonic motion.

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(c) (i)     A heat engine works at two temperatures of 27o c and 2270C. Calculate the efficiency of the engine.

(ii) temperature which will increase the efficiency by 10% if the room temperature is kept at 270C.

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8.  (A) (i) Define thermal convection.

(ii) Prove that at a very small temperature difference, ?T = Tb -Ts Newton's law of cooling obeys the Stefan's whereby Tb is the temperature of the body and Tis the temperature of the surrounding.

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(b) (i) What is meant by temperature of inversion?

(ii) A thermometer was wrongly calibrated as it reads the melting point of ice as -IO OC and reading a temperature of 60 0C in place of 500C. What would be the temperature of boiling point of water on this scale?

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9.  (a) What is meant by the following terms:

(i) Alternating current (a. c). (ii) Effective value of A. C.

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(b)     A 60 volt, 10watt lamp is to be run on 100volt, 60Hz A.C mains. (i) Calculate the inductance of a choke coil required.

image(ii) If a resistor is used in (b) (i) above instead of choke, what will be the value of its resistance?

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(c)      An LCR circuit with R = 700 in series with a parallel combination of L=1.5H and C = 30gF is driven by a 230V supply with angular frequency of 300rad/s. 

(i) Find the power in put to the circuit.

 (ii) At the frequency ? = how does the circuit respond?

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10.  (a) Define the following terms:

(i)        Current density

(ii)      Conductivity

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(b) (i) Under what condition is Ohm's law true?

(ii) Why does the voltage across the terminals of a cell or battery fall when it is delivering a current?

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 (c) (i)   Define temperature coefficient of resistance.

(ii)  A heating coil of Nichrome wire with cross sectional area of 0.1mrn2 operate on a 12 V supply, and has a power of 36 W when immersed in water at 373K. Calculate the length of the wire.

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11. (a) What is meant by the following electronic circuits:

(i)       Logic gates

(ii)      Integrated circuits.

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(b) Draw a truth table for the circuit in Figure 1 including the states at C, D, E, F and G.


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(c) Study the circuit in Figure 2 the answer the questions that follow:



(i)   What type of a single gate would provide exactly the same function as a circuit in Figure 2.

(ii)      Draw the diagram of a symbol representing a single gate in 11(c) (i).

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12.(a) (i) What is light emitting diode (LED)?

(ii)  Give three advantages of LED's lamp in radio and other electronic systems over filament lamps.

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(b) (i)What is the basic difference between good conductors and semiconductors.

image(ii) Two silicon diodes each of forward bias voltage of 0.7V are connected in a circuit as shown below:

Calculate the value of I1 and 12image

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(c) (i) Mention two types of transistors.

(ii) Which among the transistors mentioned in (c) (i) above responds quickly to electrical signal? Give reason for your answer.

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13.  (a) Give the meaning of the following terms:

(i)  Bandwidth

(ii)  Amplitude modulated carrier wave.

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(b) (i) What is the purpose of amplifiers in a phone link?

(ii) Sketch the frequency spectrum for 1500m radio waves modulated by a 4 kHz audio signal.

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width="2" height="1" alt="image">(c)(i) List down two advantages of digital signals over analogue signals.

(ii)  A carrier of frequency 800 kHz is amplitude modulated by frequencies ranging from 1 kHz to 10 kHz. What frequency range does each sideband cover?

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14.  (a) Describe the sources and effects of the following pollutants on the environment:

(i)        Air pollution

(ii)      Radiation pollution.

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(b) Briefly explain the influence of the following climatic conditions for plant growth and development:

(i) Rainfall and water. (ii) Wind.


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