Physics Paper 3 Questions and Answers with Confidential - Samia Joint Mock Examination 2023

INSTRUCTIONS TO CANDIDATES

• Answer all the questions 
• You are supposed to spend the first 15 minutes of the 2 ½ hours allowed for this paper reading the whole paper carefully before commencing your work.
• Marks are given for a clear record of the observations made, their suitability, accuracy and use.
• Candidates are advised to record their observations as soon as they are made.
• Non programmable silent electronic calculators and KNEC Mathematical tables maybe used.

QUESTION 1

You are provided with the following:

• Triangular card marked PQR
• Plastic or glass beaker
• Straight piece of wire
• Two strips of cellotape
• Optical pin
• Set square
• Stop watch

You are required to have a complete mathematical set

Proceed as follows:

1. Draw the perpendicular line to the base QR and measure and record the height PM, of the triangular card
   PM =……………………………….. (1mk)
2. Using the optical pin provided, make holes along the perpendicular line drawn such that the distance y = 10 mm, 20 mm, 30 mm, 40 mm, 50 mm and 60 mm from P.
                                                                            
3. By using a small piece of cellotape, attach both ends of the thin length of wire to the circumference of the beaker with the wire passing through the hole y = 10 mm and the card hangs freely in the figure below.
                                                        
4. Displace the card by the help of a 15 cm rule, so that it oscillates about the wire as an axis. Determine the time for 5 complete oscillations and then find the periodic time T.
   Record your values in the table below.
5. Repeat the procedure in (d) above for other values of y and complete the table appropriately. (7 mks)
   

   Y(mm)	10	20	30	40	50	60
   Time for 5 oscillations (s)
   Periodic time, T (s)

6. Plot a graph of T (y-axis) against y on the grid provided (5 mks)
                                                              
7. From the graph, determine T, the periodic time for which y = ¹/₃ (3 mks)
8. Hence, calculate the constant from the formula; t = √^Q/_K where t is the time for 5 complete oscillations when y = ¹/₃h and Q = 48.4 m (4 mks)

QUESTION 2

PART A

You are provided with the following apparatus:

• A Nichrome wire mounted on a millimeter scale
• 6 connecting wires, 2 with crocodile clips
• An ammeter
• A voltmeter
• A cell holder
• Two dry cells
• A micrometer screw gauge
  Proceed as follows:
  1. Connect the circuit as shown below. The length of the wire AB used to complete the circuit should be exactly 1 meter.
  2.  
     1. Close the switch and record the correct I and the potential difference V across the wire AB. Open the switch.
        I = …………… Amperes (1 mk)
        V = ……………Volts (1 mk)
        1. Determine the resistance R = ^V/_I, given that (1 mk)
  3. Measure the diameter, d of the wire AB using a micrometer screw gauge
     D……………m (1 mk)
  4. Determine the quality of the material of the wire from the relationship; R = ρl, where A is the cross-sectional area of the wire. (3 mks)
                                                                                                                           A
     PART B (I)
     You are provided with the following apparatus:
     • White screen
     • 100 ml glass beaker
     • A metre rule
     • A candle
     • A 100 ml measuring cylinder
     • Some water, about 100 ml, in a plastic beaker
       Proceed as follows:
  5. Using the measuring cylinder, measure 80 ml of water and transfer it into the 100 ml glass beaker.
  6. Place the 100 ml beaker with the water on a metre rule and arrange a lit candle and screen on either side of the beaker as shown in the figure below. Ensure the candle flame is in line with the water level in the beaker.
                             
  7. Set the position of the candle on the metre rule so that its centre is a distance, u = 12cm from the beaker.
  8. Adjust the position of the screen until a well focused vertical line (The image of the candle flame) is formed on the screen. Read and record in the table below, the image distance v between the screen and the beaker.
  9. Repeat the procedure for other values of u shown and complete the table appropriately.
     

     Distance u (cm)	12	16	20
     Distance v (cm)
     Y = uv        u + v

                                                                                                                                       (4 mks)
  10. Determine m, the mean value of y using the values in the table above
      m = ………………… (1 mk)
  11. With the half-metre rule outside the beaker, measure the height h, of the water meniscus above the bench.
      h = …………cm (1 mk)
  12. Determine the value of P given that: P = ⁵/_√h(1 mk)
  13. Hence determine the value of f, correct to one decimal place, given that:
                  f = ^p/_2m + 1 (2 mks)
      PART B (II)
      You are provided with the following apparatus:
      • A rectangular glass block
      • Soft board
      • Five optical pins
      • Four thumb tucks
      • Half-metre rule
        Proceed as follows:
  14. Using the half metre rule, measure the width, w of the glass block
      w = ………………cm (1 mk)
  15. Place the glass block on the plain piece of paper and draw its outline.
  16. Remove the glass block and mark a point X midway along one of the longest sides of the outline. Fix a pin P₁ on this point.
  17. Replace the glass block to fit perfectly on its outline.
  18. On the opposite side, fix two pins P₂ and P₃ on the right side of X so that they appear to be in line with the image of P₁ viewed through the longer side opposite X.
  19. Repeat step (e) but with two other pins P₄ and P₅ on the left side of X as shown in figure
  20. Remove the glass block and the pins. Draw a line joining P₂ and P₃ , then another joining P₄ and P₅. Extend the lines P₂P₃ and P₄ P₅ to intersect at y as shown in figure below.
                                 
  21. Measure the distance XY.
      XY = ………………cm (1 mk)
  22. Calculate the value given that:     (2 mks)    
                η =   w    
                     w − xy

CONFIDENTIAL

The apparatus required by each candidate for the Physics Practical Examination are listed below. It is expected that the ordinary apparatus of a Physics laboratory will be available.

The physics teacher should note that it is his/her responsibility to ensure that each apparatus acquired, for this examination agrees with specifications given.

QUESTION 1

Each candidate will require the following

• An isosceles triangular card, made from manila paper, of base length 6.0 cm and height 12.0 cm. The base is to be marked QR and the apex marked P
• A glass/plastic beaker of volume 500 ml
• A nichrome wire (gauge 22) of length equal to (d + 4) cm, where d is the maximum diameter of the beaker. The wire must be straightened
• Two strips of cellotape or masking tape
• A complete mathematical set
• A stop-watch
• An optical pin

QUESTION 2

• Rectangular glass block, measuring approximately 10 cm by 6 cm by 2 cm.
• Soft board
• Five optical pins
• Four thumb tucks
• Half-metre rule
• White screen
• 100 ml glass beaker
• A metre rule
• A candle
• A 100 ml measuring cylinder
• Some water, about 100 ml, in a plastic beaker
• A nichrome wire (gauge 32) mounted on a millimeter scale.
• 6 connecting wires, 2 with crocodile clips.
• An ammeter (0 – 1 A)
• A voltmeter (0 – 5 V)
• 2 new dry cells.
• A micrometer screw gauge (to be shared)
• A switch.

MARKING SCHEME

Question 1

(a) PM=12.0 ± 0.5 cm 1 dp

(e) 

Each correct - 1mk
All correct:3dp - 1mk
Y(mm) 10 20 30 40 50 60

(f) 
                                        

(g)  ¹/₃ h = ¹/₃ ×12=4 cm = 40 mm
       T = 0.444 s
       Shown on the graph

(h) t = 0.444 × 5 = 2.22 s   (student's value of T × 5)
       2.22²=  √^48.4/_k)  - correct substitution of student^' svalue of t
      4.9284 = ^48.4/_k - attempt to simplify
      k = 9.821 m/s²
      (9.0 − 10.5) deny for wrong units;no units but within range,1⁄2 mark

Question 2

Part A

(b) (i) I = 0.22 ± 0.02 Amperes
         V =1.9 ± 0.2 Volts

     (ii) R = ^1.9/_0.22 = 8.636 Ω

(c) d = 0.00035 m (0.35 ± 0.05 mm)

(d) 8.636      =         ρ ×1           
                        π × 0.000175² 
                  ρ = 2.645 × 10⁻⁷Ωm (3rd mark for correct unit)

(i) 

(j) m = 3.479 + 3.264 + 3.264 = 3.336 cm
                              3

(k) h = 4.8  ± 0.3 cm

(l) P =  5   = 2.282
         √4.8

(m) f = 2.282 + 1
          2 ×3.336
        = 1.342 cm

(n) w = 6.1 ± 0.2 cm

(u) XY = 2.5 ± 0.2 cm

(v) η =    6.1     
           6.1 − 2.5
        =1.694