KCSE Past Papers 2019 Physics Paper 3 (232/3)

 

 

2019 Physics paper 3

Question 1

You are provided with the following:

 

  • A stirrer
  • A stond, a boss rind a clump
  • A themionieter
  • An aninieter
  • A voltmeter
  • A beaker
  • A source of boiling water
  • Two dry cells in a cell holder
  • A switch
  • Seven connecting wires
  • A component labelled XProceed as follows:

    (a) Set up the circuit as shown in figure 1.

    Close the switch, read and record the current I through component X and the potential difference V across it. (l mark)I =……………………..

    V =……………………….

    Open the switch.

    Determine the resistance R of component X given that: R = V/I

    (b) Pour hot water into the beaker and set up the apparatus as in figure 2, so that component X afid the llieriiioirieter bulb are fully immersed.

  • (c) Stir the water from time to time, when the temperature falls to 80°, switch on the circuit, read and record the current I and the potential difference V in table 1. Then open the switch.(d) Repeat (c) as the temperature falls to the oÎher values shown in table 1. Complete the table. Table 1 (8 marks)
  • (e) ( i) On the axis provided, plot a graph of Log R against log T. (4 marks)
  • (ii) Determine the slope S of the graph. (3 marks)(ii) Given that R and T are related by the equation Log R = Log K + n Log T (4 marks)

    (i) n…………………………..(1 marks)

    (ii) k…………………………..(2 marks)

    Question 2

    You are provided with the following:

     

  • A metre rule
  • A stand, boss and clamp A piece of string
  • A 20 g mass
  • A 50 g mass
  • A measuring cylinder containing water
  • A concave mirror
  • A screen
  • A candle
  • Pieces of sewing threads
  • A mirror holder (Lens holder)Proceed as follows:

    PART A

    (a) Using a string, suspend the metre rule on the stand so that it balances horizontally at its center of gravity.

    Record the centimetre mark at which the metre rule balances.

    Centimetre mark =………………….cm (1 mark)

    (b) With the metre rule balanced at its centre of gravity, suspend a 20 g mass at a distance of 30 cm from the centre of gravity.

    Suspend the 50 g mass on the other side of the centre of gravity and adjust its position until the rule is balanced. See figure 3.

  • Record the distance d of the 50 g ninss from the centre of gravity.d = ……………………….

    d = ……………………… (1 mark)

    Record the volume of the water in the measuring cylinder provided.

    V=……………………………….(1 mark)

    (ii) Immerse the 20 g mass fully into the water and adjust the position of the 50 g mass so that the rule balances horizontally.

    Record the volume V1 of the water plus 20 g mass and the distance d1 of the 50 g mass from the centre of gravity.

    (iii) (I) Determine the volume of the water displaced (1 mark)

    (II) Determine the weight of the water displaced. (density of water — I gcm(-3) (3 marks)

    (d) (i) Use the principle of moments to determine the apparent weight of the 20 g mass when fully immersed in water. g — 10 Nkg-1 (2 marks)

    (ii) Calculate the weight of the 20 g mass in air (g = 10 Nkg-1)

    (iii) Determine the apparent loss in weight of the 20 g mass. (l mark)

    PART B

    (e) Light the candle and place it at distance u = 20 cm in front of the concave mirror. Adjust the position of the screen until a sharp image of the candle flame is obtained. See figure 4.

  • (i) Read and record the distance v between the screen and the mirror.v=………………………………(1 mark)

    (ii) Determine:

    I. The magnification m of the mirror given that: m = v/u (1 mark)

    II. the value f1 given that: f1 = mu/m+1

    (f) Repeat part (e) for distance u1 = 18 cm.

    (i) Read and record the distance v1 between the screen and the mirror. (ii) Determine the magnification m1 of the mirror. (1 mark )

    (iii) Hence determine f2.

    (g) Determine the average value of f. 1

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