PHYSICS PAPER 3 - KCSE 2019 ALLIANCE MOCK EXAMINATION

QUESTION 1

PART A

You are provided with the following apparatus:

• A rectangular glass block.
• Four optical pins.
• A soft board.
• A protractor.
• 30cm ruler.
• 2 white plain papers.
• A plane mirror.
• A vernier calipers (to be shared)

PROCEDURE

1. Trace the outline of the glass block on the white paper.
2. Draw a normal ON, 2cm from point X on side XY.
3. Measure an angle (i) 10º from the normal.
4. Place back the glass block on the outline and fix a plane mirror vertically along the length of the glass block on the opposite side of XY using a cello tape as shown in the figure below.
   
5. Fix two pins P₁ and P₂ as shown in the figure.
6. By observing image of P₁ and P₂, locate two pins P₃ and P₄ such that they appear to be in line with images of P₁ and P₂.
7. Remove the pins and the block. Join P₃P₄ and produce the line to meet line P₁P₂ produced
8. Measure the perpendicular distance y.
9. Repeat the same for angles of 15º, 20º, 25º, 30º, 35º and 40º and record the results in table 2 below.
   (NB: The paper work must be submitted together with the question paper).
   
   Table 2
   

   Angle i	10º	15º	20º	25º	30º	35º	40º
   y(cm)

   (7marks)
10. Plot a graph of y(cm) against angle i.                                                                   (5marks)
    1. Use the graph to determine y_o the value of y when i = 0º
       y_o = ……………… cm                                                                       (1mark)
    2. Measure and record the breadth (b) of the glass block
       b = ……………. Cm                                                                          (1mark)
    3. Determine the value of h given that (2marks)

PART B
You are provided with the following:-

• A boiling tube.
• Some dry sand.
• A liquid in a measuring cylinder labelled L.
• Half metre rule.
• A vernier calipers (to be shared).
• A weighing machine (to be shared).
• Tissue paper.
• A measuring cylinder.

Proceed as follows:

1. Measure the length of the boiling tube.
   h = ……………………. cm                                                                                 (1mark)
2. Put a little amount of sand in the boiling tube and place it in the measuring cylinder which is almost filled with liquid L. Add sand, little by little until the tube floats upright as shown in figure below.
   
3. Measure the length, d, of the boiling tube which is above the liquid using half metre rule
   d = …………… cm                                                                                              (1mark)
4. Determine the length, t, of the boiling tube which is immersed in the liquid using half metre rule
   t = ………….. cm                                                                                                (1mark)
5. Remove the boiling tube from the measuring cylinder, wipe it dry (on the outside) and measure its mass, m, including the sand inside.
   m = ………….. g                                                                                                  (1mark)
6. Measure the external diameter, D, of the boiling tube.
   D = ………….. cm                                                                                               (1mark)
7. Determine the external radius, R.
   R = …………… cm                                                                                             (1mark)
8. Using the formula m = 12rpR², determine r for the liquid.                           (2marks)

Question 2

You are provided with the following:-

• A 250ml glass beaker.
• A Bunsen burner.
• A thermometer.
• A stopwatch.
• A Tripod stand and a wire qauze.
• A measuring cylinder 100ml.

Procedure
Set the apparatus as shown in figure below. 

1. Measure 100cm³ of water and pour it into the beaker. Take the initial temperature of the water.
   T_o =……………… ºC.                                                                                         (1mark)
   Now heat the water to a temperature of 75ºC. Switch off the gas tap and place a thermometer into the beaker and start the stopwatch when the temperature is 65ºC. Take the temperature TºC of water every two minutes. Record your results in the table 3 below.               (7marks)
   Table 3
   

   Time, t(minutes)	2	4	6	8	10	12	14
   Temperature, T(ºC)
   (T – To) (ºC)
   Log (T – To)

2. Plot a graph of Log (T – T_o) against Time (t).                                                  (4marks)
3. From the graph find the value of Q given that Q = log (T – T_o) when t = 0.          (1mark)
4. Determine P, where P is the antilog of Q.                                                                  (1mark)
5. Calculate the temperature of the surrounding T_S using expression P = 65 - T_S.   (2marks)

MARKING SCHEME