Physics Paper 1 Questions and Answers - Asumbi Girls High School KCSE Mock 2021

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  • This paper consists of two sections A and B.
  • Answer all the questions in the spaces provided.
  • All workings must be clearly shown.
  • Mathematical tables and silent electronic calculators may be used.

Answer all the questions in this section in the spaces provided.
(Take g=10N/kg or 10m/s2)

  1. The figure1 below shows a wire wound on a test tube. The windings just touch each other. If the total number of complete loops was found to be 15, and the distance covered by the windings on the test tube is 20cm; find the radius of the wire. (2marks)
  2. A paratrooper flexes his legs when he lands. Explain (1mark)
  3. A needle may float on clean water but sinks when a detergent is added. Explain. (1 mark)
  4. The mass of a fabric of a large balloon is 100kg. the balloon is filled with 200 m3 of helium and attached to a cable fixed to the ground as shown below.
    Given that the densities of air and helium are 1.3 kg/m3 and 0.018kg/m3 respectively, determine the tension in the string. (3 marks)
  5. Water flows in a pipe of diameter 7cm at a speed of 5m/s. The water then gets to the perforated end which has 20 holes of diameter 0.7cm each.Determine the speed of water jets. (3 marks)
  6. For an enclosed system with a liquid, a force is applied at one point.
    1. Briefly explain how force is transmitted to other parts of the system. (2 marks)
    2. State one application of such a system. (1 marks)
  7. A 150g mass tied on a string is whirled in a vertical circle of radius 30cm with a uniform speed. At the lowest position the tension in the string is 9.5N.Calculate the velocity of the mass. (3 marks)
  8. A spring of elastic constant K has its length increased from 4.00m when unloaded to 4.25m when loaded with a 75N weight. Assuming that the elastic limit is not exceeded, determine the value of K. (2 marks)
  9. The figure 2 below shows a glass tube fitted on to a boiling tube filled with water. State and explain what is observed when the boiling tube is heated. (2marks)
    Figure 2
  10. A bus that carries goods in the roof carrier is less stable than one that carries goods in the boot. Explain why this is so. (1 mark)
  11. A rod consists of glass on one part and copper on the other. The rod is wrapped with a piece of paper and then a flame passed below it. It is observed that the paper on the side with glass is charred while that on the side of copper is not. Explain this observation. (1 mark)
  12. The figure 3 below shows a uniform 50cm rod. It is balanced horizontally by a load of 4N on one end. Calculate the weight of the rod. (2marks)
    fig. 3
  13. The figure 4 below shows a bimetallic strip cooled below room temperature. Sketch on the side the bimetallic strip at room temperature. (1Mark)
    Figure 4.

SECTION B (55 Marks)
Answer all questions in this section in the spaces provided.

    1. Define “absolute zero temperature” for an ideal gas (1 Mark)
    2. Using kinetic theory, explain Boyle’s law for an ideal gas. (2Marks
    3. The diagram shows an experiment to investigate the relationship between volume and temperature of a fixed mass of gas at constant pressure.
      1. Explain the function of;
        1. Concentrated sulphuric acid (1 Mark)
        2. Stirrer (1 Mark)
      2. Explain how the set up above can be used to verify Charles law for an ideal gas (3Marks)
      3. On the grid below sketch a graph of volume (cm3) against temperature (0c). Mark with letterT the absolute zero temperature. (2 Marks)
    4. A column of air 20cm long is trapped by mercury thread 6cm long as shown in figure 7 (a) below.
      If the tubeis now inverted,determine column X in figure b).Take atmospheric pressure as 76cm of mercury. (2Marks)
  2. The figure 8 below shows an experimental set up for estimating the diameter of an oil molecule.
    1. Describe how the oil patch is formed (2Marks)
      1. In this experiment the diameter ‘d’ of the oil patch was measured to be 21cm for an oil drop of radius 0.28mm. Determine the diameter of the oil molecule. (3Marks)
      2. State any two assumptions made in calculating the diameter of the oil molecule. (2Marks)
    3. What is the role of the lycopodium powder in this experiment? (1Mark)
    4. Describe one method of determining the diameter of an oil drop. (2Marks)
    1. The figure 9 below shows the pattern formed on a tape in an experiment to determine the acceleration of a trolley.The frequency of the ticker tape used was 50Hz
      Figure 9
      1. The initial velocity of the trolley (2Marks)
      2. The final velocity of the trolley (2Marks)
      3. The acceleration of the trolley (2Marks)
    2. A gun is fired vertically upwards from the top of an open truck moving horizontally at a uniform velocity of 50m/s. The bullet attains a maximum height of 45m.
      1. The time taken by the bullet to reach the maximum height (3Marks)
      2. The distance covered by the truck just before the bullet reaches the level from which it was fired. (3Marks)
    1. A man used a wooden plank to lift a wooden log from the ground to a stationary truck as shown in the figure. The wooden plank is inclined at an angle of 300 to the ground.
      1. Show that the velocity ratio of the system is given as V.R=1/〖Sin 30〗^0 (3Marks)
      2. Given that the system is 65% efficient, determine the Mechanical Advantage. (3 marks)
      3. Explain why the efficiency of this system cannot be 100%. (1Mark)
    2. The figure 11 shows a pulley system.
      1. State the velocity ratio of the machine. (1Mark)
      2. Explain what happens to the Mechanical Advantage of the machine as the load is increased gradually. (1Mark)
    3. Water drops from a waterfall to the bottom. The temperature of the water is found to be higher at the bottom than at the top.State the energy transformations. (1Mark)
    1. Define “specific heat capacity” of a substance (1Mark)
    2. In an experiment an aluminium block of mass 2kg was heated using an immersion heater as shown in figure 12 below
      The temperature of the block was recorded every minute for exactly five minutes and then the heater was switched off. A graph of temperature in 0c against time in minutes for the experiment is shown below.
      Study the graph above and answer the questions that follow.
      Suggest why;
      1. The reading in the thermometer rose relatively slowly between point A and B. (1Mark)
      2. The temperature continued to rise after the heater was switched off (1Mark)
      3. Use the straight portion of the graph (Bto C)to calculate the specific heat capacity of the aluminium given that the voltmeter read 22.00V and ammeter 10A throughout the course of the experiment. (3Marks)
    3. Explain the two reasons why the value calculated in b) iii) will not be accurate. (2Marks)
    4. A temperature scale X has an ice point of 400 and a steam point of 2400 .What is the temperature in X0 when the Celsius temperature is 500C. (3Marks)

Marking Scheme

  1. Diameter of wire 20/15 = 1.33
    Radius of wire 1.33÷2 =0.67cm
  2. To increase the time take to come to a stop which reduces the rate of change of momentum or reducing the impulsive force producing a small reaction on him by floor
  3. Clean water has a high surface tension addition of detergent reduces/breaks/lowers the surface tension
  4. Upthrust = weight + Tension
    pVg = mg + T
    1.3 x 200 x 10 = 0.18 x 200 x 10 + 1000 + T
    T =1240N 
  5. A1V1=A2V2
    π7/2 x 7/2 x5=πx20x0.7/2 x 0.7/2 xV2
    1. Pressure is developed at the point of application of the force. Since the liquid is incompressible, pressure is uniformly transmitted and force is generated.
    2. Hydraulic machines (brakes, press,lift)
  7. F=(mv2)/r+mg
    9.5=150/1000 x v2/(30⁄100)+150/1000 x10
  8. e=4.25-4.00=0.25m
  9. The level of water in the tube first drops and then rises. Due to expansion of the glass boiling tube.
  10. The c.o.g is raised when the carrier is at the top lowering the stability.
  11. Copper a good conductor of heat conducts the heat away hence paper does not char/burn.
  12. Wx5=4x20√
    1. The temperature at which the volume/ pressure/K.E of a gas is assumed to be zero.
    2. Reducing the volume increases the number of collisions of gas particles with the walls of the container per unit time. Therefore the rate of change of momentum will also increase leading an increase in pressure.
          • Serves as a pointer to the volume on scale or
          • To trap the gas in the tube or
          • A drying agent for the gas
        2. To make the temperature of the bath uniform.
      2. Heat the bath and record the temperature and height/volume of air trapped at suitable temperature interval. Plot a graph of volume/height against temperature. The graph is a straight line indicating proportional change in volume and temperature.
      3. See sketch on grid.
    4. P1V1=P2V2
    1. Introduce the oil drop on the water surface. The surface tension of water reduces and the net force of the surrounding water pulls oil molecules outwards hence spreading.
      1. Ah=volume
        πx( 21/2)h=πx 4/3 (0.028)3
        h=2.92693/110.25=2.655 x 10-7 m
      2. Oil patch is a perfect circle, a monolayer
        Oil drop is perfect sphere
    3. To make boundary of oil patch visible or
      To reduce surface tension of water
    4. Trapping oil in a loop of wire and holding it against a mm scale. View the oil drop under a magnifying lens (glass) to enable correct measurement of diameter. or
      Run known number of drops of oil from a burette, obtain the volume of one drop (volume run out/number of drops).
      Then use the formula V= πr3/3to obtain the radius hence the diameter.
    1. t=1/50=0.02seconds
      u = s/( t)=1/0.02 =50cm/s
    2. v=5/0.04 =125cm/s
    3. a=(v-u)/t=(125-50)/(0.02x4..5) =833.33cm/s2 or 
      • 8.3333ms-2    
    4. h=1/2 gt^2
      45=1/2 x10t^2 
      T=3sec = 30m/s

    5. T =2t 
      1. V.R=(Effort distance)/(load distance)
        But sinθ=BC/AB

      2. η=MA/VR x100
        65=MA/(1/sin⁡300 )x 100 √1
        65=MA/2 x100

      3. Energy is lost in overcoming frictional force on the inclined surface/plane
      1. V.R=4
      2. M.A increases as the load increases
    3. P.E → K.E → heat+sound
    1. This is the quantity of heat required to raise the temperature of unit mass of substance by one kelvin or one degree Celsius.
      1. Some of the heat is used to warm the insulating cover and surrounding area.
      2. The heater was still hot (at a higher temperature than the block) continues heating before cooling.
      3. Power supplied= IV=10x22=220W OR
        Slope=Δθ/Δt=(52-30)/((5-2)(60) )=22/180 0c⁄s 
        C=p/m x t/Δθ=220/2 x 180/22=900 j⁄kgk c = 900J/kgK
      4. Heat lost to the surrounding, heat used to warm up the insulating cover and thermometer or heat is lost to warm insulating cover and thermometer.
      5.     100-0       50-0     
          240-40        X-40

          100         50   
         200           X-40
        = 1400√1

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