Physics Paper 3 Questions and Answers - Sukellemo Joint Mock Examinations July 2020

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INSTRUCTIONS TO CANDIDATES

  1. Write your name and Adm number in the spaces provided above. 
  2. This paper consists of two questions. 
  3. Answer all the questions in the spaces provided in the question paper.
  4. All working must be clearly shown.
  5. Marks are given for a clear record of the observations actually made, for their suitability and accuracy and the use made of them. 
  6. Candidates are advised to record their observations as soon as they are made. 
  7. Non-programmable silent electronic calculators may be used in calculations. 
  8. Candidates should check to confirm that all pages are printed as indicated and no questions are missing.

FOR OFFICIAL USE ONLY

QUESTION  MAXIMUM SCORE  CANDIDATE'S SCORE
1A 13  
1B 07  
2A 11  
2B 09  
TOTAL 40  


QUESTIONS

QUESTION ONE
PART A
You are provided with the following:

  • A resistor wire mounted on a millimeter-scale.
  • An ammeter (0-2.5A)
  • A voltmeter (0-5V)
  • A switch
  • 3 dry cells in a cell holder
  • A bulb
  • 8 connecting wires (4 with clips at one end)

Proceed as follows;

  1.  Set-up the circuit as shown in figure 2.
    q1 mbvjgavhda
  2. Place the sliding clip at L = 20cm from M then close the switch. Record both the ammeter and voltmeter readings in table 1.
  3. Repeat the procedure in (b) by placing the sliding clip J at points where L = 40cm, 60cm, 70cm 80cm and 90cm from M.
  4. Record the corresponding readings of the ammeter and voltmeter in table 1.
    Table 1
    Length, L(cm)  20  40  60  70  80  90 
    Current, 1(A)            
    I, (mA)            
    Voltage, V(v)            
    V, (mV)            
    (7marks)
  5.  Plot a graph of I (mA)(y-axis) against V (mV) (3 1/2marks)
  6. Determine the voltmeter reading when the ammeter reads 0.16A (1 1/2mark)
  7. Describe the brightness of the bulb as length C (cm) increases. (1 mark)

PART B
You are provided with the following:

  • A metre rule.
  • Knife edge raised 20cm above the bench.
  • One 50g mass and 100g mass.
  • Some thread.
  • Some tissue paper.
  • Some water in a beaker.
    Liquid L in a beaker.

Proceed as follows

  1. Balance the metre rule on the knife edge. For the rest of the experiment, the knife edge must be placed at this point.
  2. Set up the apparatus as shown in figure below. Use the threads to hang the masses such that the positions of support can be adjusted.
    q1 part b jhabdc
    The balance is attained by adjusting the position of the 100g mass. Note the distance X cm and D em are measured from the knife edge and 50g mass is fully immersed in water. Determine the values of X and D.
    x = .................................cm (1/2 mark)
    D = .................................cm(1/2 mark)
    Determine the weight W1 of the 50g mass in water and its upthrust Uw in water.
    W1 = .................................cm (2 marks)
    U= .................................cm (1 mark)
    Remove the 50g mass from the water and dry it using tissue paper.
  3. Now balance the metre rule when the 50g mass is fully submerged in liquid L. Record value of the distance X
    X = .................................cm(1/2 mark)
    Determine the weight W, of the 50g mass in the liquid L and its upthrust UL in the liquid
    W2 = .................................cm (1 mark)
    UL = .................................cm(1/2 mark)
  4. Determine the relative density RD of the liquid L. (1 mark)

QUESTION 2
You are provided with the following apparatus

  • Triangular glass prism 
  • 4 optical pins 
  • Plain paper
  • A soft board
  • A source of boiling water 
  • 250 ml beaker 
  • A thermometer 
  • A stopwatch

Proceed as follows:
PART A

  1. Fix the plain sheet of paper on the soft board. Place the triangular prism on the paper and trace its outline on the sheet of paper. Remove the prism and use a ruler to extend the three sides of the outline. See figure below.
    part a jhgajgd
    Measure angle A and length C
    A= ................................. (1 mark)
    L== .................................(1mark)
    NB: The plain sheet of paper must be submitted together with the question paper.
  2. At a point about a thirdway along one side of the outline from angle A, draw a normal. (2marks)
  3. Draw a line at angle i = 40 to the normal. Stick two pins PI AND P2 vertically on the line. See Figure 3.
    figure 3 kjahhd
    Figure 3
    Place the prism accurately on the outline. By viewing through the opposite side, stick two other pins P, and P4 vertically such that they are in line with the two images of pins P1 and P2.
  4. Remove the prism and the pins. Draw a line joining the marks made by P, and PA. Extend lines P, P2 and P, PA to intersect. Hence measure the angle of deviation D.
    D= ................................... (1 mark)
  5. For two other values of angle i shown in Table 2 locate and measure the corresponding angles of deviation. Complete Table 2. (2 marks)
    40° 50°  60° 
         
  6.                      
    1. Determine the average value Dm of D (1 mark)
    2. Determine the constant K using the equation (3marks)
      f kjahghda
      PART B
      (Read all the instructions before starting this part)
  7. Using the thermometer measure and record the temperature of the room.
    T= ...................................(1 mark)
  8. Using the 250m1 beaker, collect 200ml of hot water from the boiling water source. Place the thermometer into the hot water and wait until the water cools to 80°C then start the stopwatch and record the time t, it takes the water to cool to 75°C.
    t1= ...................................(1 mark)
  9. Wait until the water cools to 70°C then start the stopwatch and record the time t2 it takes the water to cool to 65°C.
    t2= ...................................(1 mark)
  10. Determine the rate of temperature change P and Q in the two time intervals;
    P=77.5-T (2marks)
           t1
    Q=67.5-T (2 marks)
           t2
  11. State with a reason how the rate of change of temperature between 90°C to 85°C compares with P. (2 marks)

MARKING SCHEME

QUESTION 1
PART A
Table 1: Repeated values should be accepted if they fall in the range

Exact conversion from A to mA=All correct=​

Length, L (cm)  20  40  60  70  80  90 
Current, I(A) 2d.p. ±0.02 0.10 0.15 0.18 0.20 0.20 0.22 
I(MA) Exact conversion from A to mA
=All correct=  
Voltage, V(v) ldp, ±0.2 0.3 0.6 1.1 1.4 1.8 2.0
V (mV) Exact conversion from A to mA
=All correct=  

e) Plot a graph of I(MA) (y-axis) against V (mV)
1 khgad
If no mark is awarded for the curve then mark f for only showing on graph @ 1/2 mk
f) Determine voltmeter reading when the ammeter reads 0.16A

  • Showing on the graph1/2 mk
  • Correct reading with an allowance 1/2 mk
    of 1 small square. Deny % mk for missing unit

g) Describe brightness of the bulb as length (cm) increases

  • Brightness increases

PART B
Determine values of X and D

  • X = 16.5 ± 1.0(1 d.)
  • D = 40.0 ± 1.0 (1 d.)

Determine weight Wl of the 50g mass in water and its upthrust Uw in water
(must use principle of moments)

  • W1 = 1 x 16.5 =W1 x 40
    W1 = 0.4125N
  • Uw= 0.5N-0.4125N
    = 0.0875N

c) Now balance metre rule when 50gmass is fully submerged in liquid L. Record value of distance X\

  • 17.0 ± 1.0

Determine weight W2 of the 50g mass in the liquid and itsupthrust Ul in the liquid
(Must use the principle of moments)

  • W2= 1 x 17.0 = W2 x 40
    W2 = 0.425N
    (Ignore missing unit but penalize wrong unit by denying missing the X mk.)
  • U1 = 0,5N – 0.425N
    = 0.075N
    (Ignore missing unit but penalize wrong unit by denying the mk.)

d) Determine relative density Rd of the liquid L.

  • Rd = UI  0.075
            Uw     0.0875
    = 0.8571
    (accept even formula only and award 1/2 mk)
    (deny the answer mark if a unit is given)

QUESTION 2
PART A
Measure angle A and length 1

  • A = 60° ± 2°
    (deny 1/2 mk for missing unit penalized fully or wrong units)
  • L = measure the candidates L ± 0.2
    (deny 1/2 mk for missing unit penalized fully or wrong units)
    (measured value must be in the range 4.5 - 7.0 and 1 d.pa must)

c) Draw line at anglc i= 40 to the normal. Stick two pins P1 and P2 vertically on the line. See figure 3
Place prism accurately on the outline by viewing though the opposite side, stick two other pins P3 and P4 vertically such that they are in line with the two images of pins P1 and P2
2 jkgayughda
d) Hence measure the angle of deviation D

  • D = 41° ± 2° (deny 1/2 mk for missing unit penalized fully or wrong units)

e) For two other values of angle i shown in Table 2 locate and measure the corresponding angles of deviation. Complete table 2

40°  50°  60°
D 39-43 37-41 38-42
  • 3 different values of D-2 mks
  • Only 2 values of D are different - 1 mk
  • All values of D are the same - mk

f)   

  1. Determine the average value Dm of D
    • (Adding 3 values of D) 3
      From the table
      Correct value of Dm, Exact or Id.p
  2. Determine the constant K using the equation
    • Substitution
    • Evaluation (Exact or 3 s.f)
    • Accuracy 1.50 ± 0.05

PART B
g) Using thermometer measure and record the temperature of the room

  • T-15-30°C

h) Start stop watch and record the time Ti, it takes the water to cool to 75°C.

  • t1 = 120 ± 20 seconds

i) Wait until water cools to 70°C then start stopwatch and record the time t2 it takes water to cool to 65°C

  • t2 = 180 ± 20 seconds

j) Determine rate of temperature change P and Q in the two time intervals

  • P = 77.5-T
    t1
    Substitution - 1mk
    Evaluation - 1 mk
    (exact or)
  • Q = 767.5-1
    Substitution - 1mk
    Evaluation - 1 mk
    (exact or)

k) State with a reason how rate of change of temperature between 90°C to 85°C compares with P.

  • It is greater than x because the cooling rate depends on the difference between the highest temperature and room temperature

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