PHYSICS PAPER 3 Marking Scheme - 2017 MURANG'A MOCK EXAMINATION

QUESTION 1

You are provided with the following apparatus

• Two beakers.
• A complete retold stand.
• Funnel
• Cotton wool.
• Access to water.
• Stop watch.
• A burette with a tap (50cm³).
• 100ml measuring cylinder.

Proceed as follows:

1. Set the apparatus as follows:
   
   
   1. Support the burrete on a result as shown above
   2. Close the tap of the burrete and fill it with water to the brim
   3. Transfer the water to the 100ml measuring cylinder and record the volume of the water
      Volume V₁ = 65cm³   (1mk)
2. Fill the burrette with water up to the 0cm3 mark. Drain this water into 100ml measuring cylinder and record its volume V2
   V₂ = 53cm³ (1mk)
   The excess water above the zero mark is given by
   V₀ = V₁ – V₂
   V₀ = 65 – 53 = 12cm³   (1mk)
   (This volume should be added to the final volume of the burette reading when water has been drained)
3. Fill the burrete with water to the brim. Finally open the tap at once and start the stop watch simultaneously. Obtain the time, t taken for the level of water to reach X=10cm³
   Volume drained = (V₀+10) cm³
   Refill the burette with water. Finally open the tap at once and start the stopwatch simultaneously. Obtain the time taken for the level of water to reach x = 20cm3
   Volume drained = (V₀+20) cm³
4. Repeat the procedure for other values of the burette readings.
   Record the volume drained and the corresponding time in the table below.
   

   Burette reading	Volume of water drained	Time t (s)	Log10 V
   10	22	15.90	1.3424
   20	32	23.29	1.5051
   30	42	33.15	1.6232
   40	52	44.12	1.7160
   45	57	49.50	1.7559
   50	62	59.28	1.7924

   (9marks)
   1. Plot the graph of log10v (vertical axis) against time t.    (5mks)
      
      Slope =^1.88-1.3/_64-0
      =^0.58/₆₄
      = 0.009s-1
   2. Using your graph, calculate the value for b and n from the equation.   (3mark)
      Log10 V = ^4.2t/_b+n
      n= the vertical intercept
      n = 1.28
      Slope = ^4.2/_b
      b = ^4.2/_slope 
      b = ^4.2/_0.009
      = 466.755

QUESTION 2

1. You are provided with the following apparatus:
   
   • Resistance wire fitted on a scale labelled MN
   • Switch
   • Voltmeter (0.3v) or (0.5v)
   • Ammeter (0.1A)
   • Two dry cells
   • Six connecting wires
   
   
   1. Set up the apparatus as shown in the figure below
      
   2. Remove the crocodile clip from the resistance wire MN and close the switch. Record the voltmeter reading.
      Y = 2.7 V    (1mk)
   3. Attach the crocodile clip to the resistance wire such that L=10cm.
   4. Record the voltmeter and ammeter reading in the table below.
   5. Repeat the procedure in (iii) and (iv) for L= 20 cm, 30 cm, 40 cm, 50cm, 60 cm, 70cm and 80 cm.
   6. Complete the table below.
      

      Length L (cm)	10	20	30	50	80
      Current I (A)	0.86	0.48	0.43	0.255	0.205
      p.d V (V)	2.1	2.3	2.4	2.5	2.6
      Y-V	0.6	0.4	0.3	0.2	0.1
      V/Y-V	3.5	5.75	8.0	12.5	26
      V/I = R (αΎ¨)	2.4419	4.7917	5.5814	9.8039	12.6829

      (9mks)
      • At least 3 correct readings row 1 and 2 - (2mks)
      • 4-5 correct reading row 1 & 2 – (3 mks)
      • Row 3 & 4 all correct - (1mk)
   7.  
      1. Plot the graph of, vertical axis against R  (5mks)
         
      2. Determine the slope, m of the graph  (2mks)
         
      3. The graph is given by the equation
         
         Determine the value of m and d       (3mks)