Physics Paper 3 Questions and Answers - Maranda High Pre Mock Exams 2023

INSTRUCTIONS TO CANDIDATES 

• Answer ALL the questions in the spaces provided in the question paper
•  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 actually made.
• Non-programmable silent electronic calculators and KNEC Mathematical tables may be used except where stated otherwise.

QUESTION 1  

You are provided with the following: -

• 2 new size D dry cells
• A cell holder
• A switch
• An ammeter
• Five connecting wires
• Wire mounted on the metre rule labelled X
• A micrometer screw gauge (to be shared)
• A Voltmeter
  Proceed as follows
  
  1. Measure the diameter of the wire three times and determine the average diameter,
     d ……………….……………………………………… mm (1 mark)
     d………………………………………………………….. m (1 mark)
  2. Determine the cross-section area of the wire,
     A………………………………………………………….. m2 (1 mark)
  3. Connect the circuit as shown in the figure 1 below.
     
  4. Measure the voltage Efrom the Voltmeter, before closing the switch.
     E = .......................................................................... V (1 mark)
  5. Adjust the length, lof the wire to 0.20m, close the switch, S and read the value of current and record in the table 1 below.
     Table 1
     

     Length, L (m)	0.20	0.30	0.40	0.50  .	0.60	0.70
     Current, I (A)
     1/L (A−1)

  6. Repeat the procedure in (e) above for the values of lengths given. (6 marks)
  7. Calculate the value of ¹/_L and record in the table above. (1 mark) (
  8. On the grid provided plot a graph ofI¹/_L(y axis − ) against L (m) (4 marks)
  9. Determine the gradient of the graph. (2 marks)
  10. Given that the equation ¹/_L = ^P/_EAL + ^r/_E  holds for the graph, determine the value of ρ and r   (3 marks)

QUESTION 2

PART A

You are provided with the following:

• A lens and a lens holder.
• A screen with cross wires
• A candle
• A metre rule.
  Proceed as follows:
  
  1. Arrange the lightened candle, the lens and the screen as shown in figure 2. Adjust the position of the screen until a sharp inverted image of the candle is formed on the screen.
     
     1. Measure the image distance v
        v =  …………………………… cm (1 mark)
     2. Determine the focal length of the lens using the formula 
        f =   uv      (2 marks)
             u + v
  2. Now arrange the lighted candle, the screen with cross wires and the lens as shown in figure 3. Ensure that the centre of the lens, the cross-wires, and the candle flame lie on the same horizontal line. The candle flames should be placed close to the cross-wires for better illumination.
     
     1. Adjust the position of the lens until a sharp image of the cross-wire is formed on the screen next to the cross wires. (Hint: You have to rotate the lens slightly about a vertical axis so that the image of the cross-wires falls on the screen next to the cross wires and not on the cross-wires.)
        Measure the distance d, between the lens and the screen.
        d=………………………………. cm (1 mark)
     2. Determine the values of L and X:
        1. L =   df      (2 marks) 
                 f − d
        2. X =  L  + 1 (2 marks) 
                  2f

PART B

You are provided with the following:

• A metre rule
• A knife edge
• One 50g mass and a 100 g mass
• Two pieces of threads each 30 cm long
• Some water in a beaker
• Liquid L in a beaker
• Tissue paper

Procced as follows

1. Balance the metre rule on the knife edge and record the reading at this point
   Balance point = ……………………………………cm mark (1 mark)
   For the rest of this experiment the knife edge must be maintained at this position.
2. Set up the apparatus as shown in the figure 4
   Figure 4
   
   The balance is obtained by adjusting the position of 100g mass when 50g mass is fully immersed in water. Record the values of X and D.
   X =…………………………………………………… (1 mark)
   D =…………………………………………………… (1 mark)
3. Using the principle of moments;
   1. determine the weight W₁of the 50g mass in water (2 marks)
   2. determine the Upthrust U_W in water (1 mark)
4. Remove the 50 g mass from the water and dry it using a tissue paper.
   Keeping D constant, adjust the position of 100g mass until the metre rule is balanced and record the value of distance X when the 50g mass is fully immersed in liquid L.
   X =…………………………………………………….. (1 mark)
   1. Determine the weight W₂ of the 50g mass in liquid L. (2 marks)
   2. Determine the Uphtrust U_L in the liquid. (1 mark)
5. Determine the relative density R.D of the liquid L, given that R.D = U_L  (1 mark)
                                                                                                             U_W
6. Find the density of liquid L in S.I unit (1 mark)

CONFIDENTIAL

QUESTION 1  

• 2 new size D dry cells in a cell holder 
• A switch 
• Seven connecting wires at least two with crocodile clips 
• Voltmeter 0-3V or 0-5V 
• Ammeter 0-2.5A
• Nichrome wire mounted on a mm scale labelled X 
• A micrometer screw gauge (to be shared) 

QUESTION 2  

PART A  

• A lens of focal length 10 cm and a lens holder. 
• A screen with cross wires 
• A white screen 
• A candle 
• A metre rule. 

PART B  

• A metre rule 
• A knife edge 
• One 50g mass and a 100 g mass 
• Two pieces of threads each 30 cm long 
• Some water in a beaker 
• 200ml of kerosene in a beaker labelled Liquid L 
• Tissue paper

MARKING SCHEME

QUESTION 1  

You are provided with the following: -

• 2 new size D dry cells
• A cell holder
• A switch
• An ammeter
• Five connecting wires
• Wire mounted on the metre rule labelled X
• A micrometer screw gauge (to be shared)
• A Voltmeter
  Proceed as follows
  
  1. Measure the diameter of the wire three times and determine the average diameter,
     d ……………0.30 ± 0.04  ✓1….……………………………………… mm (1 mark) 2 d.p a must
     d…………^0.30/₁₀₀₀  ✓½ = 3.0 × 10⁻⁴  ✓½……………………………………………….. m (1 mark) Working must be shown( students value to be used)
  2. Determine the cross-section area of the wire,
     A……²²/₇ × (1.5 × 10⁻⁴)²  ✓½ = 7.071 × 10⁻⁸… ✓½………………………………………………….. m2 (1 mark) Working must be shown
  3. Connect the circuit as shown in the figure 1 below.
     
  4. Measure the voltage Efrom the Voltmeter, before closing the switch.
     E = ............3.0 ± 0.2.. ✓½............................................................ V (1 mark) 1 d.p a must
  5. Adjust the length, lof the wire to 0.20m, close the switch, S and read the value of current and record in the table 1 below.
     Table 1
     

     Length, L (m)	0.20	0.30	0.40	0.50  .	0.60	0.70
     Current, I (A)  2 d.p  ±0.02	0.60	0.52	0.44	0.40	0.36	0.32
     1/L (A−1)	1.667	1.923	2.273	2.500	2.778	8.333

  6. Repeat the procedure in (e) above for the values of lengths given. (6 marks)
  7. Calculate the value of ¹/_L and record in the table above. (1 mark) 
  8. On the grid provided plot a graph ofI¹/_L(y axis − ) against L (m) (4 marks)
     
  9. Determine the gradient of the graph. (2 marks)
     gradient = Δ ¹/_I (A⁻¹) = (2.35 − 1.5) A⁻¹  ✓½
                        ΔL(m)        (0.44 − 0.14)m  ✓½
                                       = 2.833A⁻¹m⁻¹ OR 2.833 (Am)⁻¹  ✓1 
  10. Given that the equation ¹/_L = ^P/_EAL + ^r/_E  holds for the graph, determine the value of ρ and r   (3 marks)
        ρ  = gradient  ✓½
       EA
                      ρ                      =  2.833(Am)⁻¹ 
      3.0V × 7.071 × 10⁻⁸ m²   (substitution)
      ρ = 2.833 A ⁻¹m⁻¹ × 3.0V × 7.071 × 10⁻⁸m² 
      ρ = 6.00964 × 10⁻⁷Ωm  ✓½ (accuracy)
      ^r/_E - y-intercept  ✓½ (equation)
      ^r/_3.0V = 1.1A⁻¹  ✓½  (substitution)
        r = 3.3 Ω   ✓½ (accuracy0

QUESTION 2

PART A

You are provided with the following:

• A lens and a lens holder.
• A screen with cross wires
• A candle
• A metre rule.
  Proceed as follows:
  
  1. Arrange the lightened candle, the lens and the screen as shown in figure 2. Adjust the position of the screen until a sharp inverted image of the candle is formed on the screen.
     
     1. Measure the image distance v
        v =  ……15.0 ± 2.0 ✓1……………………… cm (1 mark) 1 d.p a must
     2. Determine the focal length of the lens using the formula 
        f =   uv      (2 marks)
             u + v
        30 × 15.0  ✓1
        30 + 15.0
        = 10cm  ✓1
  2. Now arrange the lighted candle, the screen with cross wires and the lens as shown in figure 3. Ensure that the centre of the lens, the cross-wires, and the candle flame lie on the same horizontal line. The candle flames should be placed close to the cross-wires for better illumination.
     
     1. Adjust the position of the lens until a sharp image of the cross-wire is formed on the screen next to the cross wires. (Hint: You have to rotate the lens slightly about a vertical axis so that the image of the cross-wires falls on the screen next to the cross wires and not on the cross-wires.)
        Measure the distance d, between the lens and the screen.
        d=…………5.0 ± 4.0  ✓1……………………. cm (1 mark) 1 d.p is a must
     2. Determine the values of L and X:
        1. L =   df      (2 marks) 
                 f − d
           L = 5.0 × 10  ✓1
                  10 − 5
              = 10cm  ✓1
        2. X =  L  + 1 (2 marks) 
                  2f
           X =    10cm     + 1  ✓1
                 2 × 10cm
           x = 1.5cm  ✓1

PART B

You are provided with the following:

• A metre rule
• A knife edge
• One 50g mass and a 100 g mass
• Two pieces of threads each 30 cm long
• Some water in a beaker
• Liquid L in a beaker
• Tissue paper

Procced as follows

1. Balance the metre rule on the knife edge and record the reading at this point
   Balance point = …………50.0 ± 0.5  ✓1…………………………cm mark (1 mark) 1 d.p is a must
   For the rest of this experiment the knife edge must be maintained at this position.
2. Set up the apparatus as shown in the figure 4
   Figure 4
   
   The balance is obtained by adjusting the position of 100g mass when 50g mass is fully immersed in water. Record the values of X and D.
   X =……………17.5 ± 0.5cm… ✓1…………………………………… (1 mark)  1 d.p is a must
   D =…………40.0 ± 1.0cm… ✓1……………………………………… (1 mark)  1 d.p is a must
3. Using the principle of moments;
   1. determine the weight W₁of the 50g mass in water (2 marks)
      W₁ = 1 × 0.175   ✓½
                     0.4
         = 0.4375N  ✓1
   2. determine the Upthrust U_W in water (1 mark)
      U_W = 0.5 − 0.4375  ✓½
            = 0.0625 N  ✓½
4. Remove the 50 g mass from the water and dry it using a tissue paper.
   Keeping D constant, adjust the position of 100g mass until the metre rule is balanced and record the value of distance X when the 50g mass is fully immersed in liquid L.
   X =…………18.0 ± 0.5  ✓1………………………….. (1 mark) 1 d.p is a must
   1. Determine the weight W₂ of the 50g mass in liquid L. (2 marks)
      W₂ = 1 × 0.18  ✓1
                    0.4
            = 0.45N  ✓1
   2. Determine the Uphtrust U_L in the liquid. (1 mark)
      U_L = 0.5 − 0.45  ✓½
           = 0.05N  ✓½
5. Determine the relative density R.D of the liquid L, given that R.D = U_L  (1 mark)
                                                                                                             U_W 
   R.D =   0.05     ✓½
              0.0625
         =  0.8 ✓½
6. Find the density of liquid L in S.I unit (1 mark)
   Ρ_L = 0.8 × 1000 ✓½
        = 800kg/m³ ✓½