PHYSICS PAPER 3 - KCSE 2019 MARANDA MOCK EXAMINATION

1. PART A
   You are provided with the following apparatus .
   • Two dry cells
   • Resistance wire mounted on a mm scale
   • An ammeter (0- 1 A)
   • Cell holder
   • Voltmeter (0- 3 V )
   • 8 connecting wires, at least four with crocodile clips on one end.
   • Switch
     
     Procedure as follows:
     1. Connect the circuit as shown in the diagram below. 
        
     2. Close the switch and disconnect the clip and record the voltmeter reading E
     3. Connect the clip at c where L is 100cm across the terminals as shown in the figure and record the values on the table below
     4. Repeat the procedure c for the other values of L and complete the table
        

        Length L (cm)	95	80	65	50	35	20
        Current I (A)
        P.D. (V)
        E- V   (V)

     5. On the gridprovided plot a graph of (E – V) y-axis against I. (5 mks)
     6. Determine the slope S of the graph (2 mks)
     7. Given that E = V + Ir determine r from your graph (2 mks)
2. PART B
   You are provided with the following apparatus
   • Rectangular glass block
   • 3 optical pins
   • A soft board
   • A plane paper
   • 4 paper pins
     
     Procedure as follows:
     1. Place the rectangular glass block in the middle of the plane paper and trace its outline using a pencil. Remove the block . 
        
        Mark the point O, the mid point of BC M the midpoint of AD. Join O to M.
        Measure P₁M=P₃M = 2 cm
        Measure OM: 
     2. Place the plane paper on the soft board, stick it using the paper pinsand carefully replace the glass block so that it can fit the outline .
     3. Press the object pin at O such that it is upright and touching the glass block and the second pin at P₁ also upright and touching the block.
     4. Press the third pin P₂ a short distance from the block such that P₁,P₂ and the imageI lie on a straight line when viewed through the block with one eye.
     5. Remove the glass block and draw the line P₁P₂ to cut OM at I
     6. Repeat procedure (iii) and (iv) above with pins at P₃ and P₄.
        Measure the length IM            
     7. Find n given that n =OM/IM (2 mks)
3. You are provided with the following
   • a boiling tube
   • Some sand
   • Liquid L in a container
   • A balance
   • A half meter rule
   • Some tissue papers
   • Vernier calipers
   • A 50g mass
   • A string
   • Stopwatch
   • String
   • A retort stand
     
     Proceed as follows
     1. Measure and record the total length Y of the boiling tube 
        
     2. Put the amount of sand provided into the tube and place it in liquid L as shown below
         
     3. Measure and record the length X of the tube above the liquid level;
        make sure that the boiling tube is upright
     4. Determine the constant L given that L = Y – X (2 mks)
     5. Remove the boiling tube from the liquid, wipe it and measure the mass M of the tube and its content
     6. Using the calipers, measure the diameters d₁ and d₂ at two different positions of the boiling tube (2 mks)
     7. Determine the average d_avof d₁ and d₂                                 2mks
     8. Determine the constant and give its unit    4mks                            
        
        Part B
     9. Now use the mass provided and set it up as shown below with the length of 0.5m
        
     10. Displace the mass horizontally and release it and take the time t for 10 oscillation
     11. Determine the time T for one oscillation (2 mks)
     12. Determine the constant g given that and state its unit (4 mks)

MARKING SCHEME

QUESTION 1
PART A

1. E= 3.0 + 0.1 (1mk)
   

   Length L (cm)	100   0.12	70   0.19	60   0.20	50   0.23	40   0.28	20   0.40
   Current IA
   P.d (v)	2.60	2.50	2.40	2.40	2.30	2.00
   E-V (V)	0.4	0.5	0.6	0.6	0.7	1.0

2. Graph
   Labelled axis (both A1) (Unit must be indicated on both axis )
   Simple uniform scale – S1 (accommodate all values )
   Plotting of candidate values ½ x 4 – P2. Within 1 small square.
   Straight line with positive gradients
   Passing through at least 3 correctly plotted points – L1 with one small square.
3. Slope (no line no gradient)
   correct intervals –                                        (1 mark)
   Correct evaluation with correct units     (1 mark)
4. R – slope (1 mark)
   Answer and correct unit      (each ½ mark)

PART B

1. OM = 10.0 + 0.3 (1 mk)
   MI = 6.1 cm   (1 mark )
2.  
   
   Construction (1 mark)

QUESTION 2
PART A

1. V = Average length of test tube +2cm atleast 1dp a must (1 mk)
2. X = +2cm atleast 1 dp a must (1 mk)
3. L = Y- X
   Correct substitution V shown (1 mk)
   Correct evaluation of candidates values /difference (1 mk)
4. M = +2g atleast 1dp a must (1 mk)
5. d1/d2 = +05   atleast 2dp a must (1mk x 2)
   d_av = (d1+d2)/2       principle of averaging (1 mk)
   Correct evaluation to 2 dp (1 mk)
6. Q = 1.273/d²l - correct substitution of candidates values (1 mk)
   Correct evaluation to 2dp (1 mk)
   Accuracy Q = +   (1 mk)
   Unit g/cm³     (1 mk)

PART B

1. T = +50 sec
   Atleast 2 dp a must (1 mk)
2. T =    t/10    show division (1 mk)
   Correct division/evaluation (1 mk)

3. G = 4π²l/T² correct substitution ( π= 22/7 or 3.142)   of candidates value (1 mk)
   Correct evaluation to 1 dp (1 mk)
   Accuracy y= 10 + 0.5 (1 mk)
   Unit m/s²     (1 mk)