Physics Paper 1 Questions and Answers - Meru Central Cluster Exam 2020

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PHYSICS
PAPER 1
TIME: 2  HOURS

INSTRUCTIONS

  • This paper consist of TWO sections; A and B.
  • Answer ALL the questions in section A and B in the spaces provided.
  • ALL working MUST be clearly shown.

SECTION A – 25 MARKS (ANSWER ALL THE QUESTIONS)

  1. The verneir calipers in the figure below has a zero error of -0.05cm.
    phymerp1q1
    State the actual reading of the measuring instrument (2 marks)
  2. Fig.1(a) and (b) shows a set – up to determine the density of a liquid.
    Determining the density of the liquid. (3mks)
    phymerp1q2
  3. The figure below shows an open-ended monometer with water connected to a gas supply
    phymerp1q3
    If a mercury barometer reads 760mm, calculate the pressure of gas (give your answer in N/m3).
    (Density water = 1g/cm3, density of mercury = 13.6 g/cm3 (3 marks)
  4. An object weighs 49N on earth where gravitational acceleration is 9.8N/Kg and 40.5N on another planet. Determine the gravitational acceleration on the planet (2 marks)
  5. A measuring cylinder contains 20cm3 of water. 10cm3 of salt is added and stirred. Explain why the new volume is not 30cm3 (2 marks)
  6. The figure below shows samples of same liquid B and C being heated through a well-lagged copper rod of non-uniform thickness. A thermometer is placed on each sample for some time.
    phymerp1q4
    If the rod is heated at the middle, state and explain which of thermometers records a higher temperature (2 marks)
  7. Give one reason why boiling water cannot be used to sterilize a clinical thermometer (1mark)
  8. The figure 6 below shows a uniform 50cm rod. It is balanced horizontally by a load of 4N on one end. Calculate the weight of the rod 2mks)
    phymerp1q8
  9. Explain why a car feels lighter as it travel at a higher velocity. (2mks)
  10. Pure water at 00c is heated up to 100c. Sketch the graph of volume against temperature on the axes given below 2mks)
  11. The figure 8 below shows a circuit diagram for a device for controlling the temperature in a room.
    phymerp1q11
    1. Explain the purpose of the metallic strip 2mks)
    2. Describe how the circuit controls the temperature when the switch S is closed 2mks)

SECTION B – 55 MARKS (ANSWER ALL THE QUESTIONS)

  1.      
    1. Define the term velocity ratio of a machine (1 mark)
    2. A man pushes a load of mass 80kg up an inclined plane through a vertical height of 5m as shown below. The inclined plane makes and angle of 300 to the horizontal (take g to be 10m/s2)
      1. Determine the velocity ratio of the velocity ratio of the inclined plane. (2 marks)
        phymerp1q12bi
      2. If the efficiency of the plane is 75% determine:
        1. The mechanical advantage (2 marks)
        2. The effort E, needed to pull the load up the plane. (2 marks)
    3. A trolley of height 0.2m moving on a horizontal bench of height 3.2m strikes a barrier at the edge of the bench. The object on top of the trolley flies off on impact and lands on the ground 2.5m from the edge of the bench as shown below. Use this information to answer the questions that follow:
      phymerp1q12c
      1. Give a reason why the object on the trolley flies off on impact (2 marks)
      2. Determine the time taken by the object to land on the ground (2 marks)
  2.    
    1. state Hooke’s Law (1 Mark)
    2.    
      1. A vertical spring of un streched length of 30cm is clamped at its upper end. When sand is placed in a pan attached to the lower end of the spring its length becomes 45cm. When 20g mass is placed on top of the sand the length increases to 55cm. Determine the mass of the sand (3 marks)
      2. If the spring in (i) above is compressed from its original length to a length of 24cm, calculate the work done in compressing the spring. (3 marks)
    3. The graph below shows the relationship between (F) against extension (e) of a spring.
      phymerp1q13c
      Determine the spring constant of the spring (3 marks)
  3.      
    1. state Archimedes Principle (1 mark)
    2. Explain one application of Archimedes Principle in real life situation (2 marks)
    3. The mass of the fabric of a large balloon is 500g. The balloon is inflated with 2000m3 of helium gas. The balloon is attached to a cable tied on the ground as shown. (Density of helium and air are 0.18g/cm3 and 1.3g/cm3 respectively
      phymerp1q14c
      1. State 3 forces acting on the set up. (3 marks)
      2. Determine the tension in the cable (3 marks)
      3. Calculate the acceleration of the balloon if the cable is cut. (2 marks)
    4. The diagram below shows a hydrometer.
      phymerp1q14d
      Why is the part marked B wider? (1 mark)
  4. The diagram below shows a spring balance tied to an object of mass M and rotated in a circular path of radius r.
    phymerp1q15
    1.      
      1. State the force that keeps the object moving in a circular path. (1mark)
      2. The speed of the object is constant but the body is acceleration on the circular path. Explain (1 mark)
    2.    
      1. If the object is whirled faster, what would happen to the spring balance reading? (1 mark)
      2. Give a reason for your answer in b (i) above (1mark)
      3. As the object is whirled round, the sting snaps and cuts off. Describe the subsequent path of the object (1 mark)
    3. If the mass m of the object s 500g and radius r is 50cm. determine the velocity of the body if the spring balances reads 81N (3 marks)
  5.        
    1. State the pressure law for an ideal gas. (1 mark)
    2. The pressure P of a fixed mass of gas at constant temperature of T = 200k is varied continuously and the values of corresponding volume recorded. A graph of P against 1/v is shown on the graph below.
      phymerp1q16b
      Use the graph to:
      1. Determine the volume of the gas when pressure reads 2.8 x 105 pa (2marks)
    3. The petrol air mixture in the cylinder of a car engine is ignited when the piston is in the position shown below.
      phymerp1q16d
      Use kinetic theory of matter to explain why the piston moves down. (3 marks)
  6.        
    1. Define the term specific heat capacity. (1mk)
    2. 100g of steam of 1000C was passed into cold water at 27oC. The temperature of the mixture became 500C. Taking specific heat capacity of water as 4200jkg-1k-1 and specific latent heat of vaporization of water as 2260kjkg-1 and that heat losses were negligible. Determine
      1. quantity of heat lost by steam. (2mks)
      2. quantity of heat gained by water. (3mks)
      3. Mass of the cold water. (3mks)

MARKING SCHEME

  1. Main scale + vernier Scale + error
    2.5 + 0.04 + 0.05 = 2.59

  2. mass of the liquid = 12 – 6 = 6 g
    volume of the liquid = 9 cm3
    density of the liquid = 6/9 = 0.6667 g/cm3

  3. Gas pressure = atm pressure + hpg
    = 0.76 ×13600 ×10+0.1 ×1000 ×10
    =103360+1000=104360N/M

  4. Mass of the object = 49/9.8=5 kg
    Acc due to gravity = 40.5/5=8.1N/kg

  5. mater is made up of many tiny particle. Small particles of salt fit in between molecules of water when dissolving
  6. The thermometer in C
    The rate of conductivity of heat increases with cross-sectional area.
  7. Boiling water would burst the clinical thermometer
  8.    
    0.2 ×10=w ×40
    w= (0.2 ×10)/40=0.5N
    Total weight = 2000/1000+0.5
    2+0.5=2.5N
    tension=2.5 N
  9. the molecules of the air above the car moves at high velocity therefore lowering the pressure above the vehicle
  10.    
    phymerp1qa10
  11.    
    1. to make and break contact of the circuit. The strip bends and straiten when the metal contract or expand at different temperatures.
    2. When the switch is closed, current flows through the heater and warm air in the room, thus heating the strip, the strip bends away from the contact . This disconnect the heater, when the strip cools down, it reconnect and the process repeat itself.

Section B

  1.       
    1. The velocity is the ration of effort distance to that of load distance.
    2.    
      1. V.R = 1/sin⁡30 = 1/0.5 = 2
      2.    
        1. effeciency=(M.A)/(V.R) ×100
          75= (M.A)/2 ×100
          M.A= (75 X 2)/100
          =1.5
        2. M.A= L/E
          1.5=L/E
          1.5= 800/E
          E=800/1.5=533.33n
    3.          
      1. This due to inertia, the object tends to continue in uniform motion in a straight line
      2. S=1/2gt2 S=0.2+3.2=3.4m
        3.4=1/2 × 10t2
        t2=0.68,t=0.8246 seconds
  2.       
    1. Hooke’s law states that force applied to an elastic material is directly proportional to the extension provided elastic limit is not exceeded.
    2. F = ke
      0.2N = K ×0.1
      K= 0.2/0.1=2N/M
      F=2×0.15
      F=0.30 N
      =0.03kg or 30g
  3.     
    1. When a body is partially or totally immersed in a fluid, it experiences an up thrust equal to weight of the fluid displaced
    2. Balloons/ships (explain any one)
    3.    
      1.   
        phymerp1qa14c
      2. T = upthrust – weight
        Volume of air displaced = 2000m3
        Upthrust = 2000 X 1300 X 10
        26 X 106 N

      3. Weight of balloon + helium
        (2000 X 0.18 X 10) + (500 X 10) = 8600
        7 = 26 X 106 – 8600
        = 25991,400N
        F = Ma = resultant force
        25991400 = (500 + 360)a
        A = 30,222.56ms2
    4. To displace large volumes of the liquid hence provide sufficient upthrust.
  4.     
    1.  
      1. centripetal force
      2.     
    2.    
      1. Tension in the spring supporting the object
      2. There is change in the direction of instantaneous velocity at various points along the circular path
      3. The object moves tangentially to the circular path at that point where it cuts.
    3. Reading of spring balance = centripetal force
      MV2
        V
      81= 0.5 X V2
               0.5
      V2=81
      V=9M-S
  5.        
    1. The pressure of a fixed mass on an ideal gas is directly proportional to the absolute temperature provided the volume remains constant.
    2.    
      1. I/V=55
        v= 1/55
        V=0.01812cm3
    3. Increase in temperature causes molecules to move faster causing more number of collisions with the wall of the cylinder, for pressure to remain constant volume must increase
  6.      
    1. the quantity of heat required to raise the temperature of a unit mass of a substance by 1 degree Celsius or by 1 kelvin.
    2.    
      1. Q = MLv
        0.1 x 2 2600 000 = 226 000 J
      2. Q = MLv + MC x change in temperature = 22600 + 0.1 x 4200 x 50 = 247 000J
      3. 247 000 = m x 4200 x 23
        m = 2.557 kg

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