Physics Paper 1 Questions and Answers - Sukellemo Joint Mock 2020/2021

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SUKELLEMO JOINT MOCK
Kenya Certificate of Secondary Education
PHYSICS PAPER 1
2 hours 

Instructions to Candidates

  • Answer all the questions in the spaces provided.
  • This paper consists of 2 sections: Section A and B
  • All working must be clearly shown.
  • Non-programmable silent electronic calculators and KNEC mathematical tables may be used.

SECTION A (25 MARKS)
Answer ALL the questions in this section in the spaces provided

  1. The level of water in a burette is at 30 cm3. 400 drops of water each of volume 0.015 cm3 was removed from the burette.
    Determine the new level of water in the burette [3 mks]
  2. Calculate the temperature change of water as it falls through a height of 20 m. (Take g = 10 N/kg and s.h.c of water =4200 J/kg/K) [3 mks]
  3. State the SI unit of density [1 mk]
  4. Give a reason why heat transfer by radiation is faster than heat transfer by conduction [1 mk]
  5. A railway truck of mass 4000 kg moving at 3 m/s collides with a stationary truck of mass 2000 kg. The couplings join and the trucks move off together. Calculate their common velocity after collision. [3 mks]
  6. State the principle of moments [1 mk]
  7. An air bubble with a volume of 1 cm3 escapes from the helmet of a diver at a depth of 200 m below the water surface. What will be the volume of the bubble immediately it breaks the surface of water? (Take atmospheric pressure = 10 m of water) [4 mks]
  8. Calculate the acceleration due to gravity on a planet where an object released from rest falls through a height of 54.2 m in 1.08 s. [3 mks]
  9. State the three factors on which the rate of heat flow depends on. [3 mks]
  10. Under a driving force of 3000 N, a car of mass 1200 kg has an acceleration of 1.3 m/s2. Find the frictional resistance acting in the car. [3 mks]

SECTION B (55 MARKS)
Answer ALL the questions in this section

  1.    
    1. Explain the following as regards the solar heater:
      SekphycP1q11a
      1. Why the pipe is fixed to a dark-coloured collector plate. [1 mk]
      2. Why the pipe is made of copper [1 mk]
      3. Why the pipe is coiled several times [1 mk]
      4. Why the collector plate is fixed to an insulator. [1 mk]
      5. Why the panel front is covered with glass. [1 mk]
    2. Liquids expand when heated and contract when cooled. However this is not always true for water.
      1. What name is given to the behavior of water? [1 mk]
      2. States two importance of this behavior of water. [2 mks]
      3. State any two disadvantages of this behavior. [2 mk]
      4. A man wants to fit a brass ring onto a steel rod of diameter equal to the inner diameter of the ring. Explain how this can be achieved [2 mk]
  2. The figure below shows a hydraulic press supporting a load F.
    SekphycP1q12
    1. What properties of liquids make them suitable for use in hydraulic machines such as the one above? [2 mks]
    2. If A and a are areas of cross-section of the pistons, and the lengths of the arm are as given, find:
      1. The force Fo [3 mks]
      2. The mechanical advantage [1 mks]
      3. The efficiency of the machine [3 mks]
      4. State two reasons why the efficiency of a pulley system is always less than 100% [2 mks]
  3.    
    1. You are provided with the following:-
      • A block of wood
      • A spring balance
      • Thin thread
      • Overflow can
      • A small measuring cylinder
      • Some liquid

        With the aid of a labeled diagram an experiment to the law of floatation
    2. The diagram below shows a car acid hydrometer.
      SekphycP1q13b
      1. Indicate on the diagram above the minimum and the maximum measurement to be taken. [2 mks]
      2. State the reason why the bulb is wide. [2 mks]
    3.    
      1. Figure below shows a uniform plank of weight 20N and length 1.0m balanced by a 0.5kg mass at a distance x from the pivot point O.
        SekphycP1q13c
        Determine the value of X [2 mks]
      2. When the block is completely immersed in water the pivot O must shift by 0.05 m to the left for the system to balance. The density of water is 1000 kgm-3.Determine:
        1. The upthrust U on the block. [3 mks]
        2. The volume of the block. [2 mks]
  4.    
    1.    
      1. Distinguish between elastic and inelastic collisions. [2 mks]
      2. A body of mass 5 kg is ejected vertically to a height of 7.2 m from the ground when a force acts on it for 0.1s. Calculate the force used to eject the body.[3mks]
    2. Explain why the moon is said to be accelerating when revolving around the earth at constant speed [2mks]
    3. A stone is whirled in a vertical circle as shown in the figure below using a string of length 40 cm. A, B, C and D are various positions of the stone in its motion. The stone makes 2 revolutions per second and has a mass of 100g.
      SekphycP1q14c
      1. Calculate:
        1. The angular velocity [ 3mks]
        2. The tension on the string at position A [3 mks]
      2. At C where the stone has acquired a constant angular speed, the string cuts. The stone takes 0.5 seconds to land on the ground. How high is point C above the ground. [2 mks]
      3. How far does it travel horizontally before hitting the ground. [2 mks]

MARKING SCHEME

SECTION A (25 MARKS)
Answer ALL the questions in this section in the spaces provided

  1. The level of water in a burette is at 30 cm3. 400 drops of water each of volume 0.015 cm3 was removed from the burette.
    • Volume of drops =(400 x 0.015)cm3 = 6cm3

      Determine the new level of water in the burette [3 mks]
    • New level = (30+6)=36cm3

  2. Calculate the temperature change of water as it falls through a height of 20 m. (Take g = 10 N/kg and s.h.c of water =4200 J/kg/K) [3 mks]
    • G.P.E = Heat again
      Mwgh = MwCwΔθ
      10 x 20 = 4200Δθ
      Temperature change Δθ = 0.0476ºC

  3. State the SI unit of density [1 mk]
    • Kilograms per cubic metre
  4. Give a reason why heat transfer by radiation is faster than heat transfer by conduction [1 mk]
    • Radiation is propagated by means of e.m waves while conduction involves movement of particles which are prone to distraction through collisions.
  5. A railway truck of mass 4000 kg moving at 3 m/s collides with a stationary truck of mass 2000 kg. The couplings join and the trucks move off together. Calculate their common velocity after collision. [3 mks]
    • m1u1 + m2u2 =(m1 + m2)
      4000 x 3 + 0= 6000v
      v= 2m/s

  6. State the principle of moments [1 mk]
    • Sum of clockwise moments about a point is equal to the sum of anticlockwise moments about the same point.

  7. An air bubble with a volume of 1 cm3 escapes from the helmet of a diver at a depth of 200 m below the water surface. What will be the volume of the bubble immediately it breaks the surface of water? (Take atmospheric pressure = 10 m of water) [4 mks]
    • P1V1 = P2V2
      P1 = (200 +10)m
      V1 = 1cm3
      P2 = 10m
      v2 = ?
      210m x 1cm3 = 10m x V2
      v2 = 210/10
      =21cm3

  8. Calculate the acceleration due to gravity on a planet where an object released from rest falls through a height of 54.2 m in 1.08 s. [3 mks]
    • s= ut + 1/gt2
      54.2 = 0 +1/g x 1.082
      g= 92.94m/s2

  9. State the three factors on which the rate of heat flow depends on. [3 mks]
    • Length of the conductor
    • The cross section area of the conductor
    • The material of the conductor
    • Temperature difference of the ends of a conductor

  10. Under a driving force of 3000 N, a car of mass 1200 kg has an acceleration of 1.3 m/s2. Find the frictional resistance acting in the car. [3 mks]
    • F=ma
      1200 x 1.3
      F= 1560N
      F = 3000 -1560
      1440N

SECTION B (55 MARKS)
Answer ALL the questions in this section

  1.    
    1. Explain the following as regards the solar heater:
      SekphycP1q11a
      1. Why the pipe is fixed to a dark-coloured collector plate. [1 mk]
        • To get heated faster since dark is a good absorber and emitter
      2. Why the pipe is made of copper [1 mk]
        • To conduct heat needed for heating water.

      3. Why the pipe is coiled several times [1 mk]
        • To increase the surface area for heating
      4. Why the collector plate is fixed to an insulator. [1 mk]
        • To minimize heat losses to the environment
      5. Why the panel front is covered with glass. [1 mk]
        • To prevent escape of the reflected radiant heat which has a longer wavelength

    2. Liquids expand when heated and contract when cooled. However this is not always true for water.
      1. What name is given to the behavior of water? [1 mk]
        • Anomolous expansion of water.
      2. States two importance of this behavior of water. [2 mks]
        • Enables the survival of aquatic during winters
        • Enables weathering of rocks to take place.

      3. State any two disadvantages of this behavior. [2 mk]
        • Can cause accidents in water transportation
        • Can cause pipe bursts

      4. A man wants to fit a brass ring onto a steel rod of diameter equal to the inner diameter of the ring. Explain how this can be achieved [2 mk]
        • Heat the ring to allow its diameter increase. Fix the rod into the hole and allow the two to cool.

  2. The figure below shows a hydraulic press supporting a load F.
    SekphycP1q12
    1. What properties of liquids make them suitable for use in hydraulic machines such as the one above? [2 mks]
      • Incompressible
      • Non-errosive

    2. If A and a are areas of cross-section of the pistons, and the lengths of the arm are as given, find:
      1. The force Fa [3 mks]
        • Fa/0.01 = 700/0.2
        • Fa = 35N
          Fo x 1 = Fa x 0.2
          Fo = 35 x 0.2
          =7N

      2. The mechanical advantage [1 mks]
        • M.A = L/E
        • 700/7
        • M.A = 100

      3. The efficiency of the machine [3 mks]
        • VR = V.Rl x VRh
          0.2/0.01 x 1/0.2

          V.R = 100
        • M.A/V.R x 100%
        • 100/100 x 100%

      4. State two reasons why the efficiency of a pulley system is always less than 100% [2 mks]
        • Part of the applied effort is raising the blocks
        • Some energy is overcoming friction between the moveable parts
  3.    
    1. You are provided with the following:-
      • A block of wood
      • A spring balance
      • Thin thread
      • Overflow can
      • A small measuring cylinder
      • Some liquid

        With the aid of a labeled diagram an experiment to the law of floatation

      • Measure the weight of blocks of wood in air
      • Fill the overflow can with the liquid and let the excess liquid flow out then place an empty measuring cylinder below the spout
      • Place the block of wood in the overflow can and measure the volume of the displaced liquid inside the cylinder
      • Using the density of the liquid, calculate the mass and then weight of the displaced liquid
      • Compare the weight of the block with the value of the weight of the displaced liquid

    2. The diagram below shows a car acid hydrometer.
      SekphycP1q13b
      1. Indicate on the diagram above the minimum and the maximum measurement to be taken. [2 mks]
        • Q- minimum
        • P- maximum

      2. State the reason why the bulb is wide. [2 mks]
        • To displace the large volume of liquid to provide sufficient upthrust necessary for floating.
    3.    
      1. Figure below shows a uniform plank of weight 20N and length 1.0m balanced by a 0.5kg mass at a distance x from the pivot point O.
        SekphycP1q13c
        Determine the value of X [2 mks]
        • 20(0.5 -x) = 5x
          x = 0.4m

      2. When the block is completely immersed in water the pivot O must shift by 0.05 m to the left for the system to balance. The density of water is 1000 kgm-3
        Determine:
        1. The upthrust U on the block. [3 mks]
          • F x 0.45= 20 x 0.05
            F = 2.222
          • U = 5 - 2.222
            U = 2.778N

        2. The volume of the block. [2 mks]
          • U = pVg
            1000 x 10 x v = 2.778
            V= 2.778 x 10-4m3
  4.    
    1.    
      1. Distinguish between elastic and inelastic collisions. [2 mks]
        • For elastic collision, both K.E and momentum are conserved while for inelastic collision only momentum is conserved.

      2. A body of mass 5 kg is ejected vertically to a height of 7.2 m from the ground when a force acts on it for 0.1s. Calculate the force used to eject the body.[3mks]
        • v2 = u2 - 2gs
          0= u2 - 2 x 10 x 7.2
          u= 12m/s
          v=0
        • Ft = momentum
          F= 5 x 12/0.1
          =600N

    2. Explain why the moon is said to be accelerating when revolving around the earth at constant speed [2mks]
      • Because instantenous change in velocity in terms of direction

    3. A stone is whirled in a vertical circle as shown in the figure below using a string of length 40 cm. A, B, C and D are various positions of the stone in its motion. The stone makes 2 revolutions per second and has a mass of 100g.
      SekphycP1q14c
      1. Calculate:
        1. The angular velocity [ 3mks]
          • w = 2πf
          • 2 x 3.142 x 2
          • 12.568 rads-1
        2. The tension on the string at position A [3 mks]
          • TA = mrw2 = mg
          • 0.1 x 0.4 x 12.5682 - 0.1 x 10
          • TA = 5.318N

      2. At C where the stone has acquired a constant angular speed, the string cuts. The stone takes 0.5 seconds to land on the ground. How high is point C above the ground. [2 mks]
        • h = 1/2gt2
          0.5 x 10 x 0.52
          h= 1.25m

      3. How far does it travel horizontally before hitting the ground. [2 mks]
        • v=wr
          12.568 x 0.4
          5.027m/s
        • R = ut
          5.027 x 0.5
          2.514m

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