PHYSICS Paper 1 Questions and Answers - Form 3 End Term 1 Exams 2023

QUESTIONS
SECTION A 

1. State any two forces that acts between two objects not in contact. (2mks)
2. State two physical characteristics that change when a metal cube is heated. (2mks)
3. The diagram below shows jets from two holes at the side of a tank filled with water. Explain why Jet A is longer than B (2mks)
   
4. State the law of conservation of linear momentum (1mk)
5. State physical quantities whose SI units are shown below. (2mks)
   NM
   Kgm/s
   M³/s
   J/kg K
6. The system below was used to balance a mass of 25kg fixed at a distance of Xm from the pivot. Find the value of X to 2.d.p. (3mks)
   
7. State two circumstances under which an object floats on a liquid. (2mks)
8. In the graph below sketch the graph of pressure experienced by a ball moving from the bottom of  a tank of water towards the surface. (3mks)
   
9. Two springs A and B. have the same length and same diameter. When the same object was suspended from the bottom of each spring separately, there was a difference in their extensions. State two factors that may have caused the difference extensions (2mks)
10. A road surface offers friction of 32,000N, to a vehicle of mass 2500kg running on it. Find the coefficient of kinetic friction of the road. Explain if the value obtained will change when it rain. (3mks) 
11. In a laboratory experiment, it was realized that two different gases of equal volume diffused across a chamber at different rates. What may have caused the difference? (2mks)
12. State one physical change that affects the speed of sound in air. 1mks

SECTION B:

13. The following results were found by a student in a bid to determine the relationship between the extensions of a spring to the load hooked on its end
    

    Mass (kg)	0	0.02	0.04	0.06	0.08	0.10
    Reading (mm)
    Force (iv)
    Extension (m)

    1.  
       1. Complete the table above for the values of force F (N) and Extension e(cm) (2mks)
       2. On the grid provided, plot a graph of force against extension (5mks)
       3. From the graph determine the spring constant (2mks)
    2. What would be the extension when a mass of 0.045 kg is hanged from two such springs in series? (2mks)
14. The diagram below shows a glass prism and incident ray striking the surface XY
    
    1.  
       1. Indicate on the diagram the path of the emergent ray. (3mks)
       2. Calculate the refractive index of the glass prism given that the critical angle of glass is 42⁰. (3mks)
    2. State ONE condition necessary for total internal reflection to occur. (1mk)
    3. State ONE application of total internal reflection (1mk)
15. The figure below shows a velocity the graph for the motion of a body of mass 5kg.
    
    1. Use the graph to determine the
       1. Displacement of the body after 12 seconds (3mks)
       2. Acceleration after point C (3mks)
       3. Force acting on a body in part a (ii) (3mks)
    2. Sketch a displacement time graph for the motion from point B to D (2mks)
16.  
    1. State Newton second law of motion (1mk)
    2. A body of mass 100kg is accelerated from a velocity of 2m/s to 5 m/s in 6 seconds. Calculate
       1. Its initial momentum (2mks)
       2. Its final momentum. (2mks)
       3. The resultant force acting on the body. (2mks)
    3.  A bullet of mass 0.01kg travelling horizontally at 100m/s. penetrates a fixed block of wood and comes to rest in 0.02 second. Calculate.
       1. The distance of penetration of the bullet into the wood. (3mks)
       2. The average retarding force exerted by the wood on the bullet. (2mks)
17. A student stands at a distance 400 from a wall and claps two pieces of wood. After the first clap the student claps whenever an echo is heard from the wall. Another student starts a stopwatch at the first clap and stops it after the twentieth clap. The stopwatch records a time of 50 seconds. Find the speed of sound. (3mks)
18. The figure below show a displacement time graph for a wave motion.
    
    What is the frequency of the wave? (2mks)
19. Give a reason why water is not a suitable liquid for use in a barometer. (1mk)
20. An oil drop of radius 0.42 mm when placed in water spreads out to form a circular patch of radius 42 cm using this information. 
    1. Calculate
       1. Volume of oil drop (2mks)
       2. Area of oil patch. (2mks)
       3. Diameter of oil molecule (2mks)
    2. State one assumption made in this experiment (1mk)

MARKING SCHEME

SECTION A 

1. State any two forces that acts between two objects not in contact. (2mks)
   • Gravitional force
   • Magnetic force
   • Electronic force
2. State two physical characteristics that change when a metal cube is heated. (2mks)
   • Volume
   • Density
3. The diagram below shows jets from two holes at the side of a tank filled with water. Explain why Jet A is longer than B (2mks)
   
   • Has smaller cross-sectional area than B
4. State the law of conservation of linear momentum (1mk)
   
   • Total momentum before collition is equal to total momentum after collition.
5. State physical quantities whose SI units are shown below. (2mks)
   NM- momentum of force
   Kgm/s- momentum
   M³/s- flow rate
   J/kg K- specific heat capacity
6. The system below was used to balance a mass of 25kg fixed at a distance of Xm from the pivot. Find the value of X to 2.d.p. (3mks)
   
   
   • Sum of clockwise = sum of anticlockwise
          Moment                        moment
   • 40 sin 30º(2.2x)  = 2.5 x 10x x    (1mk)
   • 44=230x
   • X=44/230  = 0.19M
7. State two circumstances under which an object floats on a liquid. (3mks)
   • Object is less dense than the liquid.
   • Object displaces liquid equal to its weight
   • Object placed carefully and slowly on the surface ( may be accepted)
8. In the graph below sketch the graph of pressure experienced by a ball moving from the bottom of  a tank of water towards the surface. 
   
9. Two springs A and B. have the same length and same diameter. When the same object was suspended from the bottom of each spring separately, there was a difference in their extensions. State two factors that may have caused the difference extensions (3mks)
   • Differentiate number of turns per unit length
   • Nature of material used to make spring
   • Thickness/area of cross section of material
10. A road surface offers friction of 32,000N, to a vehicle of mass 2500kg running on it. Find the coefficient of kinetic friction of the road. Explain if the value obtained will change when it rain. (3mks) 
    • Fr = NkR=NkMg      = 1.28
    • Nk=Fr/mg =    32000    Nk will descrease since fraction reduces
                          2500 x 10 
11. In a laboratory experiment, it was realized that two different gases of equal volume diffused across a chamber at different rates. What may have caused the difference? (3mks)
    • Differences in  density
    • Differences in temperature
    • Difference in pressure
12. State one physical change  that affects the speed of sound in air. 1mks
    • Temperature. Sound travels faster in hot air than in cold air
    • Humidity velocity of sound in air increase with humidity wind.

SECTION B:

13.  
    1.  
       1.  
          

          Mass (kg)	0	0.02	0.04	0.06	0.08	0.10
          Reading (mm)	120	131	139	149	161	171
          Force (N)	0	0.2	0.4	0.6	0.8	1.0
          Extension (m)	0.0	0.11	0.19	0.29	0.41	0.51

       2. Axis = 1 mk (correctly labeled)
          Scale – simple and uniform – 1mk
          Correct plotting – ½ mk each to maximum 2mks
          Line – straight line, passing through 4 correctly plotted prints – 1mk
       3. Spring constant = slope of graph
          Correct interval – 1mk
          Correct evaluation – 1mk
          Correct unit 1mk
    2.  e = 2 x ^F/_K
14.  
    1.  
       1.  
          
       2. n =¹/_{sin c}
          n = 1.494
    2. Ray passes from optically denser medium to rarer medium
       -Critical angle is exceeded
    3. Prism periscope
       - Optic fibre
15.  
    1.  
       1. Displacement = area under the curve
          =¹/₂ × 20 × 8 + 20 × 4 
          = 160 m
       2. a = ^{(v - m)}/₄
          a = ^{(0 - 20)}/₄
          a = -5m/s²
       3. F = ma
          = 25N
    2. 
       
16.  
    1. The rate of change of momentum of a body is directly proportional to applied force and takes place in the direction of the force
    2.  
       1. Initial momentum = 100 x2
          = 200 kgm/s
       2. Final momentum = 100 x 5
          = 500 kgm/s
       3.  F = m
          =³⁰⁰/₆ = 50N
    3.  
       1. v = u + at
          a = - 5000 m/s²
          v² = u² + 2as
          s= 1m
       2. F = ma
          = -50N
17. Speed = ^2d/_t
    = 320 m/s
18. f = ^2.5/_0.02
    = 125 Hz
19. Due to its low density, the tube needed is very long (10m long tube)
20.  
    1.  
       1. V = ⁴/₃πr³
          = ⁴/₃ × 3.142 × (0.21)³
          = 0.31038mm³
       2. A = πr²
          = 3.142 x (420)²
          = 554248.8 mm²
       3. V = Ah
          0.31038 = 554248.8 x h
          h = 5.6 x 10^-7 mm