Physics Paper 3 Pre Mock Questions and Answers - Mokasa I Joint Examination July 2021

Instructions

• Write your name, admission number, class and signature in the spaces provided at the top of the page.
• Answer all the questions in the spaces provided in this 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 your start.
• Marks will be given for clear record of observations actually made, for their suitability and accuracy, and the use made of them.
• Candidates are advised to record their observations as soon as they are made.
• Electronic calculators and mathematical tables may be used.

FOR EXAMINER’S USE ONLY

QUESTIONS

1. You are provided with the following apparatus.
   • Voltmeter
   • A resistance wire, W mounted on a mm scale
   • Two dry cells and cell holders
   • 6 connecting wires
   • A switch
   • A jockey
   • Micrometer screw gauge (to be shared)
     Proceed as follows:
     
     1. Connect your apparatus as shown in the figure below
        
     2. Measure the diameter, d of the resistance wire using a micrometer screw gauge.
                    d ……………………………………………………………………………….mm    (1/2 mark)
                    d ………………………………………………………………………………m        (1/2 mark)
     3. Place the jockey at L = 10cm, close the switch S. Read and record in the table the voltmeter reading.
     4. Repeat the procedure in (c) for other values of L and complete the table (7 marks)
        

        Length, L. (cm)	10.0	20.0	30.0	40.0	50.0	60.0
        Voltmeter, V(V)
        1/L(m-1)
        1/V(V-1)

     5. Plot a graph of ¹/_V((y-axis) against ¹/_L (5 marks)
        
     6. Determine the slope, S of the graph  (3 marks)
     7. Given that the y-intercept C = ¹/_E, find the value of E.  (2 marks)
     8. Given that slope S is given by S = πd² / βE find the value of β  (2 marks)
2. You are provided with the following apparatus:
   • 1 rectangular glass block
   • 4 optical pins
   • 4 thumb tucks
   • 1 soft board
   • 1 plain paper
     Proceed as follows:
     1. Fix the plane sheet of paper on a soft board using thumb tucks as shown in the figure below
        
     2. Place the glass block on the sheet of paper so that it rests on its broader face and trace the outline PQRS.
     3. Remove the glass block.
     4. Draw a perpendicular to PQ at 0 such that PO is about ¼PQ.
     5. Draw a line AO such that angle x = 15⁰
     6. Replace the glass block.
     7. Stick two optical pins P₁ and P₂ on the line AO.
     8. While looking through the glass block from side, SR, stick pins P₃ and P₄ such that they appear to be in a straight line with the images of pins P₁ and P₂.
     9. Remove the glass block and pins.
     10. Draw a line through the holes made by pins P₃ and P₄ to meet SR at C.
     11. Join C to O.
     12. Measure and record angle, y.
     13. Repeat procedure (e) to (l) for x = 25⁰, 30⁰, 40⁰, 50⁰ and 60⁰ and tabulate the data
     14.  Complete the table for values of sin (90⁰ – x) and cos y.  (8 marks)
         

         X(0)	150	250	300	400	500	600
         Y(0)
         Sin(90 – x)
         Cos y

     15.  Plot a graph of cos y (y-axis) against sin (90⁰ – x).(5 marks)
         
     16. Find the slope, S, of the graph.  (3 marks)
     17. Given that, t cos y = sin(90⁰ – x), where t is a constant, use your graph to find the value of t. (2 marks)
     18. Identify the significance of constant, t  (1 mark)
         NB: Hand in the trace-out together with your question paper

MARKING SCHEME

1. 
   
   1. Connect your apparatus as shown in the figure below
      
   2. Measure the diameter, d of the resistance wire using a micrometer screw gauge.
                  d ……………………0.3………………………………………………………….mm    (1/2 mark)
                  d ……………………0.0003…………………………………………………………m        (1/2 mark)
   3. Place the jockey at L = 10cm, close the switch S. Read and record in the table the voltmeter reading.
   4. Repeat the procedure in (c) for other values of L and complete the table (7 marks)
      
      

      Length, L. (cm)	10.0	20.0	30.0	40.0	50.0	60.0
      Voltmeter, V(V)	0.80	1.25	1.55	1.75	1.90	2.00
      1/L(m-1)	10	5	3.333	2.5	2	1.667
      1/V(V-1)	1.25	0.8	0.6452	0.5714	0.5263	0.5

   5. Plot a graph of ¹/_V((y-axis) against ¹/_L (5 marks)
      
      • Axis  1mark
      • Scale  1 mark
      • Plotting  2 Marks
      • Line  1 Mark
   6. Determine the slope, S of the graph  (3 marks)
      = 0.09426^m/_v
   7. Given that the y-intercept C = ¹/_E, find the value of E.  (2 marks)
      slope = 0.33/v
      E= 3.03v
   8. Given that slope S is given by S = πd² / βE find the value of β  (2 marks)
      =1.0e-6
2. You are provided with the following apparatus:
   1 rectangular glass block
   4 optical pins
   4 thumb tucks
   1 soft board
   1 plain paper
   Proceed as follows:
   1. Fix the plane sheet of paper on a soft board using thumb tucks as shown in the figure below
      
   2. Place the glass block on the sheet of paper so that it rests on its broader face and trace the outline PQRS.
   3. Remove the glass block.
   4. Draw a perpendicular to PQ at 0 such that PO is about ¼PQ.
   5. Draw a line AO such that angle x = 15⁰
   6. Replace the glass block.
   7. Stick two optical pins P₁ and P₂ on the line AO.
   8. While looking through the glass block from side, SR, stick pins P₃ and P₄ such that they appear to be in a straight line with the images of pins P₁ and P₂.
   9. Remove the glass block and pins.
   10. Draw a line through the holes made by pins P₃ and P₄ to meet SR at C.
   11. Join C to O.
   12. Measure and record angle, y.
   13. Repeat procedure (e) to (l) for x = 25⁰, 30⁰, 40⁰, 50⁰ and 60⁰ and tabulate the data
   14.  Complete the table for values of sin (90⁰ – x) and cos y.  (8 marks)
       
       

       X(0)	150	250	300	400	500	600
       Y(0)	51	52.5	54.5	61	64	69
       Sin(90 – x)	0.9659	0.9063	0.866	0.766	0.6428	0.5
       Cos y	0.6293	0.6088	0.5807	0.4848	0.4384	0.3584

   15.  Plot a graph of cos y (y-axis) against sin (90⁰ – x).(5 marks)
       
       • Axis  1mark
       • Scale 1 mark
       • Plotting 2 Marks
       • Line  1 Mark
   16. Find the slope, S, of the graph.  (3 marks)
       =0.6666
   17. Given that, t cos y = sin(90⁰ – x), where t is a constant, use your graph to find the value of t. (2 marks)
       =1.5
   18. Identify the significance of constant, t  (1 mark)
       = Refractive index if the glass block
       NB: Hand in the trace-out together with your question paper