Kenya Certificate of Secondary Education(KCSE) Physics 2009 PAPER 1

SECTION A (25 marks)
Answer all questions in this section in the spaces provided

1. In an experiment to measure the density of a liquid, a student filled a burette with a liquidto the 0 cm³ mark. Figure 1 shows a section of the burette showing the level of the liquid after 54.5 g of the liquid had been run out.
   
   
   Determine the density of the liquid          ( 3 marks)
   
   
2. In an experiment to determine the acceleration due to gravity, g, a student measured the period, T, and length L, of a simple pendulum. For a length L = 70.5 cm, the period T obtained as 1.7s. Given that T = 2π√ ^_L/_g, determine the value of g correct to two significant figures.        ( 2 marks)
   
   
3. A steel needle when placed carefully on water can be made to float. When a detergent is added to the water it sinks. Explain this observation.
   
   
4. Figure 2 shows two cylinders containing a liquid and connected with a tight-fitting flexible tube. The cylinders are fitted with air- tight pistons A and B as shown.
   
   
   When equal forces, F, are applied on the pistons as shown, it is observed that piston A moves up while B moves down. Explain this observation. (2 marks)
   
   
   
5. Two identical beakers A and B containing equal volumes of water are placed on a bench. The Water in A is cold while in B it is warm. Identical pieces of potassium permanganate are placed gently at the bottom of each beaker inside the water. It is observed that the spread of colour in B is faster than in A. Explain this observation.  ( 2 marks)
   
   
6. A clinical thermometer has a constriction in the bore just above the bulb. State the use of this constriction.
   
   Use the following information to answer questions 7 and 8.
   
   Two identical empty metal containers P and Q are placed over identical Bunsen burners and the burners lit. P is dull black while Q is shiny bright. After each container attains a temperature of 100⁰C the burners are turned off. Identical test tubes containing water are suspended in each container without touching the sides as shown in Figure 3.
   
   
7. Explain why the container Q may become hot faster than P.    ( 2 marks)
8. Explain why the water in test- tube in P becomes hot faster than in Q. ( 2 marks)
   
   
9. Figure 4 shows a uniform cardboard in the shape of parallelogram.
   
   Figure 4
   
   Locate the  centre of gravity of the cardboard ( 1 mark)
   
   
10. The three springs shown in figure 5 are identical and have negligible weight. The extension produced on the system of springs is 20 cm.
    
    
    
    Determine the constant of each spring          ( 2 mks)
    
    
11. Figure 6 shows two inflated balloons hanging vertically on light threads.
    
    Figure 6
    
    When a stream of air is blown in the space between the balloons, they are observed to move towards each other. Explain this observations.  ( 1 mark)
    
    
12. Figure 7 (a) shows the acceleration – time graph for a certain motion.
    
    On the axes provided in figure 7 (b), sketch the displacement – time graph for the same motion.  ( 1 mark)
    
    
13. State what is meant by absolute zero temperature (zero Kelvin or -273⁰C). (1 mark)
    
    
14. A turntable of radius 8 cm is rotating at 33 revolutions per second. Determine the linear speed of a point on the circumference of the turntable. (3 marks)
    
    SECTION B (55 MARKS)
    Answer all the questions in this section in the spaces provided.
    
    
15. 1.  State two factors that affect the boiling point of a liquid.  ( 2 marks)
    2. 100g of a liquid at a temperature of 10⁰C is poured into a well lagged calorimeter. An electric heater rated 50W is used to heat the liquid. The graph in figure 8 shows the variation of the temperature of the liquid with time.
       
       
       
       
       1.  From the graph, determine the boiling point of the liquid  ( 1 mark)
       2. 1. Determine the heat given out the by the heater between the times t= 0.5 minutes and t= 5.0 minutes        ( 2 marks)
          2. From the graph determine the temperature change between the times t = 0.5 minutes and t= 5.0 minutes        ( 1 mark)
          3. Hence determine the specific heat capacity of the liquid ( 2 marks)
             
             
       3. 1.8 g of vapour was collected from above the liquid between the times t= 6.8 minutes and t= 7.3 minutes. Determine the specific latent heat of vaporization of the liquid.        ( 4 marks)
          
          
16. 1. Define the term efficiency of a machine        ( 1 mark)
    2. Figure 9 shows a drum of mass 90 kg being rolled up a plane inclined at 25⁰ to the horizontal. The force F applied is 420N and the distance moved by the drum along the plane is 5.2 m.
       
       
       
       Determine:
       1. The work done by the effort          ( 3 marks)
       2. The work done in raising the drum        ( 3 marks)
       3. The efficiency of the inclined plane as a machine    ( 2 marks)
          
          
17. 1. State the law of flotation        ( 1 mark)
    2.  Figure 10 shows a rectangular metal block of density 10500 kgm^-3 and dimensions 30 cm x 20 cm x 20 cm suspended inside a liquid of density 1200 kgm^-3by a string attached to a point above the liquid. The three forces acting on the block are the tension T, On the string, the weight W, of the block and the upthrust, U due to the liquid.
       
       
       
       
       1. Write  the expression relating T, W and U when the block is in equilibrium inside the liquid. ( 1 mark)
       2. Determine the weight, W of the block        ( 3 marks)
       3. Determine the weight of the liquid displaced by the fully submerged block. ( 2 marks)
       4. Hence determine the tension, T in the string      ( 1 mark)
          
          
    3. A certain solid of volume 50 cm³ displaces 10 cm³ of kerosene (density 800 kgm^-3) when floating. Determine the density of the solid.    ( 4 marks)
       
       
18. 1. State the pressure law for an ideal gas      ( 1 mark)
    2. An air bubble is released at the bottom of a tall jar containing a liquid. The height of the liquid column is 80 cm. The volume of the bubble increases from 0.5 cm³ at the bottom of the liquid to 1.15 cm³ at the top. Figure 11 shows the variations of pressure, P, on the bubble with the reciprocal of volume ¹/_v, as it rises in the liquid.
       
       
       1. State the reason why the volume increases as the bubble rises in the liquid Column    ( 1 mark)
       2. From the graph, determine the pressure on the bubble:
          1. At the bottom of the liquid column;      ( 2 marks)
          2. At the top of the liquid column      ( 1 mark)
             
             
       3. Hence determine the density of the liquid in kgm^-3( 3 marks)
       4. What is the value of the atmospheric pressure of the surrounding? ( 1 mark)
          
          
    3. A rubber tube is inflated to pressure of 2.7 x 10⁵Pa and volume 3800 cm³ at a temperature of 25⁰ C. It is then taken to another place where the temperature is 15°C and the pressure 2.5 x 10⁵ Pa. Determine the new volume.   ( 4 marks)
       
       
19. 1. Define angular velocity            ( 1 mark)
       
       
    2. Three masses are placed on a rotating table at distances 6 cm, 9 cm and 12 cm respectively from the centre of rotation. When the frequency of rotation is varied, it is noted that each mass slides off at a different frequency of rotation of the table. Table 1 shows the frequency at which each mass slides off.
       
       Table 1
       
       
       1. State two factors that determine the frequency at which each mass slides off. ( 2 marks)
       2. Oil is now poured on the table before placing the masses. Explain the effect of this on the frequency at which each mass slides off. ( 2 marks)
          
          
    3. Figure 12 shows a flywheel of radius 14 cm suspended about a horizontal axis through its centre so that it can rotate freely about the axis. A thread is wrapped round the  wheel and a mass attached to its loose end so as to hang at a point 1.26m above the ground.
       
       
       
       When the mass is released, it accelerates at 0.28 ms^-2. Determine the angular velocity of the wheel just before the mass strikes the ground.( 4 marks)