PHYSICS PAPER 1 - KCSE 2019 ALLIANCE MOCK EXAMINATION

SECTION A: 25marks

1. The figure below shows part of micrometer screw gauge with 50 divisions on the thimble scale. Complete the diagram to show a reading of 5.73mm.            (2 marks)     
              
2. A bottle containing a smelling gas is opened at the front bench of a classroom. State the reason why the gas is detected throughout the room. (1 mark)
3. The figure below shows beaker containing a block of ice. 
   
    State and explain the change in stability when the ice melts.                                 (2marks)

4. An aero plane is moving horizontally through still air at a uniform speed. It is observed that when the speed of the plane is increased, its height above the ground increases. State the reason for this observation.                                  (2 marks)
5. A steel ball of mass 0.05kg was placed on top of a spring on a level ground. The spring was then compressed through a distance of 0.2m.
   
   If the spring constant is 15N/m. Calculate the maximum height reached when the spring is released.  (3marks)

6. The figure below shows a uniform metre rule of weight 3N supporting two weights. The metre rule is pivoted somewhere such that it is horizontally balanced. (Pivot not shown)
   
    The 6N weight is at 15cm mark while the 4N weight is at 70cm mark. Determine the position of the pivot from zero cm mark.        (3 marks)

7. State one environmental hazard that may occur when oil spills over a large surface area of the sea. (1 mark)
8. The figure shows a flat bottomed flask containing some water. It is heated directly with a very hot flame. Explain why the flask is likely to crack.            (2marks)
                      

9. The figure below shows a cylindrical container having hot water at 95^oC. End A is shiny while end B is dull black. At equal distances from the container is placed two identical gas jars fitted with thermometers X and Y.  Compare the readings of the two thermometers after two minutes                           (1 mark)
   

10. Give a reason for your answer in question 9 above                                            (1 mark)
11. The figure below shows the change in volume of water in a measuring cylinder when an irregular solid is immersed in it.
    
    Given that the mass of the solid is 268g, determine the density of the solid in SI units. (3 marks)

12. The following figure shows a rod made of wood on one end and metal on the other end suspended freely with a piece of thread so that it is in equilibrium.
    
    The side made of metal is now heated with a Bunsen flame. State with a reason, the side to which the rod is likely to tilt        (2 marks)

13. The spiral springs shown in the figure below are identical. Each spring has a spring constant, k = 300N/m
    
    Determine the total extension of the system. (Take the weight of the cross bars to be negligible)   (2 marks)

SECTION B: 55marks

14.  
    1. State the Archimedes principle.                                                                   (1 mark)
    2.  A rubber envelope of a hydrogen filled balloon having volume of 2m³ is held in position by a vertical string as shown below. The mass of the balloon is 1.3kg. Given that density of hydrogen is 0.1kg/m³ density of air is 1.3kg/m³.
       
       Calculate
       1. the total weight of the balloon including the hydrogen gas.                               (2 marks)
       2. the up thrust.         (2 marks)          
       3. the tension in the string.                                                                                    (2 marks)
    3. A solid weighs 50N in air and 44N when complete immersed in water. Calculate
       1. Relative density of the solid.             (2 marks)
       2. Density of the solid.          (2 marks)
15.  
    1. The figure below shows a displacement-time graph of the motion of a particle.
       
       Describe the motion of the particle in the region.      (3marks)
       OA
       AB
       BC
    2. State the Newton’s first law of motion.                                                             (1 mark)
    3. The figure below shows a trolley moving towards a barrier at a constant velocity of 20m/s. Use this information to answer the questions that follows.     
            
       1. Sketch the path followed by the object after the impact                                       (1mark
       2. Give a reason why the object on the trolley flies off on impact.                          (1 mark)
       3. Determine the time taken by the object to reach the ground.                            (2 marks)
       4. Determine the horizontal distance covered by the object from the point of impact to the point where it reached the ground.        (2 marks)
16.  
    1. What is meant by absolute zero temperature?                                               (1 mark)
    2. The set up below was used by a group of form three students to verify pressure law.
       
       Describe briefly how the set-up can be used to verify pressure law.                       (4 marks)
    3. A 4.5cm³ bubble released at the bottom of a dam measured 18cm³ at the surface of the dam. Work out the depth of the dam taking atmospheric pressure to be 10⁵ Pa and the density of water as 1g/cm³.        (3marks)
17.  
    1. One of the factors that affect the centripetal force is the mass of the body. State another factor.   (1mark)
    2. A mass of 400g is rotated by a string at a constant speed V in a vertical circle of radius 100cm. The tension in the string is 9.2N which is experienced at point T. 
       
       
       1. Determine the velocity V of the mass at point T.             (3marks)
       2. Determine the tension in the string at the bottom of the circle. (2marks)
    3. State two applications of circular motion                                                            (2marks)
18. The figure below shows an inclined plane, a trolley of mass 30kg is pulled up a slope by a force of 100N parallel to the slope. The trolley moves so that the centre of mass C travels from points A to B. 
    
    
    1. What is the work done on the trolley against the gravitational force in moving from A to B?               (2marks)
    2. Determine the work done by the force in moving the trolley from A to B         (2 marks)
    3. Determine the efficiency of the system.                                                             (3 marks)
    4. Determine the mechanical advantage of the system.                                         (3 marks)
19.  
    1. Explain why it is advisable to use a pressure cooker for cooking at high altitudes. (1 mark)
    2. A block of metal of mass 150g at 100°C is dropped into a lagged calorimeter of heat capacity 40J/K containing 100g of water at 25° The temperature of the mixture is 34°C. (specific heat capacity of water = 4200J/kg/K).
       Determine:
       1. Heat gained by the calorimeter.     (2marks)
       2. Heat gained by water.    (2marks)
       3. Specific heat capacity of the metal block.    (3marks)

MARKING SCHEME

1.  
   
2. Diffusion
3. Stability increases, position of cog lowers
4. Increase in the speed of the plane increase the speed of air in the opposite direction, lowering the pressure above the plane.
5. 1/2mv²=mgh
   1/2x15x0.2=0.5x10xh
   h=0.3m
6. F₁d₁+F₂d₂=F₃d₃
   6d=3(35-d)+4(55-d)
   d=25cm

7. death of aquatic life.
8. because of unequal expansion of glass,the outside expands before the inside.
9. Y records higher reading than X,
10. Dull surfaces are better emitters of heat than shinny.
11. 140-96=44
    ρ=m/v
    =268/44
    =6.091
    =6091kg/m³

12. Heating increases the length, increasing the turning effect, tilt anticlockwise
13. F=ke
    90/300=0.3
    0.3/2+0.3/3
    0.25m

14.  
    1. when a body is partially or totally immersed in a fluid, it experiences an up thrust equal to the weight of the fluid displaced.
    2.  
       1. W=mg+vρg
          =1.3x10+2x0.1x10
          =15N
       2. U=weight of the fluid displaced/vvρg
          =2x1.3x10=26N
       3. T=U-W
          =26-15=9N
    3.  
       1. R.D=weight of solid/up thrust
          =50/6
          =8.3333
       2. Density =R.Dx density of water
          =8.3333x1000
          =8333.3kg/m³

15.  
    1.  
       1. OA-Body moving at constant velocity
       2. AB-Body at rest
       3. BC-body moving at velocity  increasing non uniformly
    2. A body remains in a state of rest or in uniform motion in a straight line/uniform velocity unless acted upon by an external force.
    3.  
       1.  
             
       2. inertia
       3. h=ut+1/2gt²   u=0
          3.2=1/2x10xt²    ,t=0.8sec
       4. S=ut
          20x0.8=16m

16.  
    1. temperature at which the volume of a body is assumed to be zero.
    2. Record the initial temperature and pressure.
       Record the temperature and the corresponding pressure at regular intervals of time
       Tabulate the results for pressure and absolute temperature in a table,
       draw a  graph of pressure versus absolute temperature
    3. P₁V₁=P₂V₂
       (10⁵+hρg) 4.5=10⁵x18
       h=40m

17.  
    1. radius of the bend
       Angular velocity
    2.  
       1. T=mv²/r - mg
          9.2=0.4v²-4
          v =3.6056 m/s
       2. T=F_c + mg  ,F _c = (0.4X3.6056²) + 4 = 9.2014N
       3. merry go round
          speed governors
          centrifuge

18.  
    1. W=FxD
       =300X10=3000J
    2. W=FxD
       =100X10/sin 15=3864J
    3. ŋ = work output/work inputx100%
       =3000/3864x100%=77.64%
    4. M.A .  =L/E
       =300/100
       =3

19.  
    1. build-up of pressure in the cooker, rising the boiling point. use less energy to cook.
    2.  
       1. Q = Cq
          = 40 x (34 – 25) = 360J                                                                                                            
       2. Q = MCq
          = 100 x 10ˉ³ x 4.2 x 10³ x (34 – 25)
          = 3780J                                                                                                                   
       3. Heat lost = 360 + 3780
          = 4140J                                                                                                                    
          MCq = 4140
          C = 418.18Jkgˉ¹kˉ¹