Physics Paper 3 Questions and Answers - Mathioya Mock 2021 Exams

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INSTRUCTION TO CANDIDATES.

  • You are not allowed to start working with the apparatus for the first 15 minutes of the 2 ½ hours allowed in this paper.
  • This time is to enable you read the questions and make sure you have all the apparatus needed.
  • Marks are given for a clear record of the observations actually made, their suitability and accuracy, and the use made of them.
  • Candidates are advised to record their observations as soon as they are made.
  • Mathematical tables and electronic calculators may be used.

FOR EXAMINER’S USE ONLY.

 Question

Maximum score

Candidate’s score

1

20

 

2

20

 

Total Score

40

 


QUESTIONS

  1. You are provided with the following
    • One stand
    • One boss
    • One clamp
    • Two pieces of thread.
    • One stopwatch
    • One metre rule or half metre rule
    • Two identical springs
    • Six 100g masses
    • A piece of cellotape.
      1 dsdsdsds
      1.                    
        1. Hang the springs from rod of a clamp as shown in the figure above.
        2. Tie together the upper end and the lower ends to springs with pieces of thread as shown in the figure.
        3. Hand a 100g mass from the lower ends of the springs so that the mass is supported by both springs.
        4. Clamp the rule vertically with zero centimeter mark uppermost.
        5. Use cellotape to fix the optical pin on the top of the 100g mass so that it acts as a pointer.
        6. Adjust the rule so that the pointer is at 40.0cm mark from the top of the rule.
      2.                        
        1. Add a 100g mass to the first mass. Record the new position of the pointer and the extension, e, in the table below.
        2. Add another 100g mass and record the new position of the pointer and the extension in the table.
        3. Repeat b(ii) until the total mass supported by the spring is 600g.
      3.                        
        1. Remove the rule. Displace the 600g mass slightly downwards and release it to oscillate vertically.
        2. Time 20 oscillations. Record in the table the time t1 for 20 oscillations. Repeat this to obtain the average time, t and the period of oscillation T.
        3. Repeat (c) i) and (ii) for 500g, 400g, 300g and 200g masses.
        4. Complete the table. (8mks)

          Mass (g)

          100

          200

          300

          400

          500

          600

          Position of point (cm)

                     

          Extension e, (cm)

                     

           Time for 20 oscillations

          t1 (s)

                     

          t2 (s)

                     

          Average time tav (s)

                     

          Periodic time, T(s)

                     

          T2(S2)

                     
      4.                         
        1. On the gird provided plot a graph of T2 (Vertical axis) against the extension, e. (5mk
          graph auygduyad
          Determine the gradient of the graph. (3mks)
        2. The equation of the graph is given by.
          ii xfsfsfsfs
          Where b and c are constants. Determine the value of b. (3mks)
        3. What does the value of b represent? (1mk

2. PART A
You are provided with the following apparatus.

  • Two dry cells.
  • Nichrome wire mounted on a mm scale.
  • An ammeter
  • Cell holder
  • Voltmeter
  • 8 connecting wires
  • Metre rule
  • Switch.

Proceed as follows.

  1. Connect the circuit as shown in the diagram below.
    2 ddadadad
  2. Connect the end A and C where AC is 100cm across the terminals as shown. Close the switch and measure both current I and p.d V across the wire AC.
    Current I = ……………………………A ( ½ mk)
    p.d V= …………………………….V ( ½ mk)
  3. Measure the e.m.f of the cells E=……………………….V ( ½ mk)
  4. Reduce the length AC. In each case record the current I and the corresponding V.
    Complete the table below. (5mks)

    Length

    100

    70

    60

    50

    40

    20

    Current I (A)

               

     p.d (V)

               

    E-V (V)

               
  5. Plot a graph of (E-V) against I (A) (5mks)
    graph auygduyad
  6. Determine the slope of the graph. (2mks)
  7. Given that E = V + Ir determine r from your graph. (1 ½ mks)

PART 2
You are provided with the following apparatus.

  • Rectangular glass block.
  • 3 optical pins
  • A soft board
  • A plane paper
  • 4 paper pins

Place the rectangular glass block in the middle of the plane paper and trace its outline using a pencil remove the block.
part 2 aygdada
Construct a perpendicular line LMO bisecting the shorter sides of M and O. Mark points P and Q such that PM = MQ = 4cm.

  1. Measure OM………………………………………………………………………..(1mk)
    • Place the plane paper on the soft board and carefully replace the glass block so that it fit the outline.
    • Press the object pin on O such that it is upright and touching glass block and the second pin on P also upright and touching the block.
    • Press the third pin P1 a short distance from the block such the P1 P and I lie on a straight line when viewed through the block with one eye. I is the image of the object pin O.
    • Repeat the experiment with now on Q. Press the third pin P2, a short distance from the block such that when viewed P2, Q and I lie in a straight line.
  2. Remove the pins and glass block; draw the lines P1 P (dotted) and P2 Q doted meeting OM at I.
    IM=……………………………………………………….…cm (1mk
  3. Using the above information calculate the refractive index of the glass block by real and apparent depth method. (2mks)


MARKING SCHEME.

(8mks)

Mass (g)

100

200

300

400

500

600

 

Position of point (cm)

Correct pointers reading to at least 1dp (1mark)

Extension e, (cm)

Correct working of extension (1dp)

 2 marks (3 correct -1mark; all correct 2marks)

 Time for 20 oscillations

t1 (s)

Correct value to 2dp.       ( 1 mk)

t2 (s)

Correct value to 2dp        ( 1 mk)

Average time tav (s)

Correct value to 4 s,f       ( 1 mk)

Periodic time, T(s)

Correct value to 4 s,f       ( 1 mk)

T2(S2)

Correct value to 4 s,f      ( 1 mk)

Gradient = correct evaluation 1 mark
=  0.04  s2/cm ± 0.001 (1mark) (wrong units no mark/no units ½ mark)
T2 = 4π2e + c
          b
Substitution of the slope i.e slope = 4π2 1mark
                                                                b
Evaluation 1mark
Correct answer range 960-1020 cm/s2  (wrong units no mark/no units ½ mark)
b- represents the acceleration due to gravity or gravitational field strength/constant 1mark
2. PART A
B) Current I = 0.12 ± 0.1  ( ½ mk)
p.d(v) = 0.26 ± 0.2  ( ½ mk)
C) E = 3.0 ± 0.01 ( ½ mk)
D) (5mks)

Length L (cm)

100

70

60

50

40

20

   

Current I (A)

0.12

0.19

0.20

0.23

0.28

0.40

± 0.1

2mk(At least 2dp

P.d. (v)

2.6

2.5

2.4

2.4

2.3

2.0

± 0.2

2mk(At least 1dp

E- V (V)

 

 

 

 

 

 

 

1mk Values to at least 1 d.p.

e) Graph
Labelled axis (both – A1)
Scale – simple and uniform and accommodating all points (S1) = both scale.
Plotting ½ each x 4 = P2 (At least 4 pts)

  • 2pts – (P1)tpt = ½ mk
  • Straight line with positive gradient passing through at least 3 correctly plotted points = L1

f) Slope (No line no gradient)

  • Correct intervals – 1mk
  • correct evaluation with unit.  (1mk)
  • Wrong unit (0mks)

No unit but correct evaluation. (½ mk)
g) r = slope.
Answer and correct unit. (½ mk)

Q2 PART B
OM = 11.7   ± 0.2 cm  to at least 1 d.p  (1mk)
MI = 7.8 ± 0.2 cm      1mk
Refractive index =     Real depth       =   OM (1mk
                               Apparent depth        IM
 OR   11.7 
          7.8
= 1.50 ± 0.2 values to at least 1 d.p  (1mk)
Construction  (1mk)
(TOTAL MARKS (5mks)

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