Physics Paper 3 Questions and Answers - Momaliche Pre Mock Exams 2023

• 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, their suitability, accuracy and the use made of them.
• Candidates are advised to record their observations as soon as they are made.
• Non-programmable silent electronic calculators and KNEC mathematical tables may be used.

1. You are provided with the following apparatus:-
   • Two meter rules
   • Two stands and two clamps
   • Two bosses
   • Three pieces of thread (at least 30cm each)
   • One optical pin
   • A piece of cello tape and a plasticine
   • A spiral spring
   • One mass of 200g
   • One stop watch
     1. Set the apparatus as shown in the diagram 1. Below ;Attach the pin (to act as the pointer)at one end of the meter –rule using cellotape or plasticine;
        
     2. Suspend one end of the metre –rule with thread at 5cm mark from the end .
     3. Suspend the other end with a spring also 5cm from the end so that metre rule is horizontal.
     4. Hold the other rule (with the spring)vertical on the beneath so that it is near the end with a pointer as shown in the diagram.
     5. Read the pointer position  .Lo=…………………………….cm, (1mk)
     6. Hang on the horizontal l metre rule, the 200g mass at a length, L =10cm from the spring.
        Record the extension, e of the spring in the table below.
     7. Displace the mass slightly downwards and release it to oscillate vertically. Take time for 20 oscillations and record in the table below.
     8. Repeat for other position of L, of the mass.
        N/B before taking the reading, ensure the oscillation is steady. (8mks)
        

        L(cm)	Extension e(cm)	Time (+) for 20 oscillation	Periodic table T(s)	T2(s2)
        10.0 20.0 30.0 40.0 50.0

     9. On the grid provided plot  a graph of extension, e (m) y-axis against T²(s²)(5
     10. Calculate the gradient of the graph drawn (3mks)
     11. Given that e =  RT² +C , determine the value of R (3mks)
                                 4π²
2. You are provided with the following
   • An ammeter
   • A voltmeter
   • Two dry cells size D
   • A mounted resistance wire on a metre-rule or millimeter scale
   • A bulb on bulb holder
   • A cell holder
   • A switch
   • A jockey or crocodile clip
   • Micrometre screw gauge (can be shared)
     1.  
        1. Connect the apparatus provided as shown in the circuit diagram below diagram 2.
           
        2. With the crocodile clip at P take the voltmeter reading and the ammeter reading,  Record V and I, Repeat the readings for L=80,60,40,20 and 0, respectively.
           Complete the table below. (4mks)
           

           Length l(cm)	Voltage v(v)	Current I(A)
           100 80 60 40 20 0

        3. What changes do you observe on the bulb as L decreases from P? (1mk)
        4. On the grid provided plot the graph of Ammeter reading (y-axis) against voltmeter reading.(5mks)
        5. Determine the slope of your graph at v =1volt. (3mks)
        6. What physician quantity is represented by the slope of the graph at the point in (v)above (1mk)
     2.  
        1. Given the apparatus in a (i) above, draw a diagram of the circuit you would use to determine the current through the resistance wire and potential differences across it .(1mk)
        2. Set up the circuit you have drawn using the available apparatus in a(i) above.
           Record the ammeter reading I and voltmeter reading v, when L =100cm. (2mks)
           V =………………………………………
           I = ………………………………………
        3. Using a micrometer screw gauge provided, measure the diameter d of the wire.(1mk)
        4. Calculate the quantity P = 0.785 (^V/_I) (^d/_L)² and give its SI units, where L is IM.(2mks)

CONFIDENTIAL

• Each candidate should be provided with the following set of apparatus.

Question one

• Two meter- rulers
• Two stand
• Two bosses
• Two clamps
• Three pieces of thread 30cm each.
• A piece of celltape or plastic line
• One mass of 200g
• A stop watch
• Spiral spring of length (4-6cm), diameter 1cm

Question two

• Two dry cells size D 1.5v each
• One bulb 2.5-3.0 volts
• Voltmeter (0 - 3v or 0 - 2.5v)
• Ammeter (0 - 2.5A)
• A switch
• Seven connecting wires (at least two with crocodile clips)
• Nichrome wire 325WG mounted on a meter rule or millimeter scale.
• Micrometer screw gauge (to be share)

MARKING SCHEME

1. (e) L_o = 56.0cm (It may depend on its position the student tied the meter – rule)
    (h)      

• Axes with scale ✔✔2
• Plot 4-5 corr ✔✔2
• Plot 3 corr ✔1
• Best line ✔1

(j) Gradient = Δe  
                      ΔT² 
                   = (4.3 − 1.4) × 10⁻²
                        (1.5 − 0) × 10⁻¹
                   = 0.19m/s² ± 0.05

(k) C = O
Gradient =  R   
                  4π²
           R = 1.9 × 4 × 3.142 × 3.142
               = 75.028m/s²

2. a) (ii)

• Axes ✔1
• Scale ✔1
• Plot 4-5 corr ✔✔1
• Plot 2-3 corr ✔1
• Curve ✔1

(v) Tangent at v = 1 volt✔1
         0.16 − 0.14
           1.4 − 0.3
Slope of tangent = 0.018Ω⁻¹

(b) (i)