Physics Paper 1 Question and Answers - KCSE 2020 Past Papers

THE KENYA NATIONAL EXAMINATIONS COUNCIL
Kenya Certificate of Secondary Education
232/1 PHYSICS Paper 1 (THEORY)

Instructions to Candidates

1. Write your name and index number in the spaces provided above.
2. Sign and write the date of examination in the spaces provided above.
3. This paper consists of two sections; A and B.
4. Answer all the questions in sections A and B in the spaces provided.
5. All working must be clearly shown in the spaces provided in this booklet.
6. Non-programmable silent electronic calculators may be used.
7. Candidates should check the question paper to ascertain that all the pages are printed as indicated and that no questions are missing.
8. Candidates should answer the questions in English.

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

1. The diameter of a wire was measured as 2.43 mm. Name the instrument that was used to measure this diameter ( 1 mark)
2. Figure 1 shows a capillary tube dipped in mercury in a beaker.
   
   
   State with a reason the observation that would be made on the level of mercury in the capillary tube if the temperature of mercury is increased. (2 marks)
3. State the kinetic theory of gases. (1 mark)
4. Figure 2 shows the scale of a measuring instrument.
   
   
   
   1. Determine the reading indicated.(1 mark)
   2. State  the physical quantity measured by this instrument.(1 mark)
5. Figure 3 shows a traditional stool resting on a level surface.
   
   
   1. ldentify its state of equilibrium.( 1 mark)
   2. State the reason for the answer in (a).( 1 mark)
6. Figure 4 shows a uniform rod AB of length 1m and weight 8N pivoted at 20 cm from one end. It is balanced by supporting it with a string attached to a fixed support.
   
   
   The tension in the string is 4N. Determine the position of the string from end A. (3 marks)
7. Define cohesive forces.( 1 mark)
8. Two similar containers A and B are filled with equal masses of water at the same temperature Container A is made of copper while container B is made of glass. Heat is then supplied to the containers at the same rate. State with a reason, the container in which water boils first. (2 marks)
9. Figure 5 shows a roof of a house over which wind is blowing.
   
   
   
   It was observed that, when the speed of the wind increased, the roof was blown off. Explain this observation. (2 marks)
10.  Figure 6 shows the velocity-time graph of the motion of a stone thrown vertically upwards.
    
    
    From the graph, determine the maximum height reached by the stone.( 3 marks)
11. It is observed that when methylated spirit is poured on the palm, the palm feels colder as it dries up. Explain this observation. (2 marks) 
12. Figure 7 shows a box placed on a weighing balance. The balance is placed on the floor of a lift.
    
    State what would be observed on the reading of the balance when the:
    1. lift is accelerating downwards(1 mark)
    2. lift moves downwards with a uniform velocity (1 mark)
    3. lift is accelerating upwards(1 mark)
13. An object placed on the surface of water in a beaker starts to sink immediately. It is observed that it stops sinking when half of its volume is below the water surface. State the reason for this observation. ( 1 mark)

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

14.  
    1. Figure 8 shows a bucket filled with water and tied to one end of a string which is used to whirl it in a vertical circular path with a uniform speed v.
       
       
       
       1. State two forces acting on the bucket at any instant. (2 marks)
       2. Explain why the tension is lowest at point A. (2 marks)
       3. The speed of the bucket is gradually reduced. Explain what is likely to be observed when the bucket is at point A.(2 marks)
    2. A stone of mass 40g is whirled at the end of a string in a horizontal circular path at (b) speed of 12ms^-1. (The string and the stone are in the same horizontal plane). If the string is 1m long, determine the tension in the string. (3 marks)
15.    
    1. Figure 9 shows a setup used by a student to investigate howa siphon works.
       
       
       1. State what would be observed when the student sucks the tube at point A and releases it. (2 marks)
       2. Explain the observation in.(2 marks) 
    2. Figure 10 shows a test-tube inverted and floating inside a plastic bottle containing some water. The bottle is then sealed.
       
       It is observed that when the sides of the bottle are squeezed, the test-rube sinks. 
       Explain this observation.(3 marks)
    3. A metallic box weighs 188N and measures 10cm by 30 cm by 8 cm. Determine the maximum pressure it can exert when lying on one of its surfaces.(3 marks)
16.    
    1. Figure 11 shows a setup that can be used to verify Charles' Law.
       
       
       1. Explain how the:
          1. temperature of air in the tube is measured;(2 marks)
          2. volume of air in the tube is measured. (2 marks) II.
       2. State how the pressure is kept constant during the experiment.
       3. State how the measurements in (i) can be used to verify Charles' law. (3 marks)
       4. State one precaution that must be taken to ensure that the temperature of air is accurately measured.(1 mark)
    2. A fixed mass of gas initially at 20°C is heated at constant pressure until its volume doubles. Determine its final temperature.(4 marks)
17.    
    1. Figure 12 shows a simple machine.
       
       
       On the same figure, mark and label the following parts:
       1. Effort arm (1 mark)
       2. Load arm (1 mark)
    2.  Figure 13 shows a pulley system used to raise a mass of 5 kg through a height of 2 m when a force of 60N is applied. (Acceleration due to gravity g is 10ms^-2)
       
       
       Determine the:
       1. distance moved by the effort; (1 mark) .
       2. work done on the load; (3 marks)
       3. potential energy gained by the load (g = 10 Nkg^-1). (1 mark)
    3. Figure 14 shows a setup that can be used to determine the specific latent heat of vaporisation of water. A beaker containing some water was placed on a weighing balance and an immersion heater rated 500 W immersed in the water.
       
       The water was then heated until it boiled. When the water started boiling, the initial the balance was reading on noted and the stop watch started immediately. The final was then noted reading on the balance after a time t seconds.
       1. State how the mass of steam can be measured using this setup. (1 mark)
       2. Write down an expression for the heat supplied by the heater. (1 mark)
       3. Determine the specific latent heat of vaporisation of water.(3 marks)
18.    
    1. State the meaning of the term matter (1 mark)
    2. Its observed that when a liquid is heated its volume increases. Explain this observation  using the kinetic theory of matter(3marks)
    3. Figure 15 shows a setup used to study Brownian motion in liquids.
       
       
       
       1. State the function of the hand lens. (1 mark)
       2. State what is observed on the pollen grains. (1 mark)
       3. Explain the observation made in (ii). (2 marks)
       4. State and explain what would be observed on the pollen grains if the water is heated. (3 marks)

MARKING SCHEME

SECTION A

1. Micrometer screw gauge
2. The level rises - cohesive forces become weaker on heating
3. It states that gases are made up of tiny invisible particles/molecules whcih are in constant random motion./ continuous - reject matter
4.   
   1. 9.5 Pa ( unit can be ignored)
   2. Pressure
5.   
   1. Stable equilibrium
   2. Returns to original  position after slight displacement - slight displacement means c.o.g doesnt go over the base hence doesn't topple over.
6. Sum of clockwise moments = sum of anticlockwise moments
    4 X x = 8 X 30
   4x= 240
   x=60
   position of string = 60 + 20 = 80cm=0.8m
7. Forces of attraction between molecules of the same type
8.    
   • Container A
   • It's a better heat conductor( comparison is a must)
9. Due to the shape, the wind at the top moves at a higher speed creating a region of low pressure at the top. The pressure difference between the top and the inside produces an upward force causing the roof to blow off.
10. at maximum height v = 0
    displacement = area under the graph
    =20m
     alternatively:
    v2 = u² - gh
    0= 20² - 2 x 10h
    h= 400 
           20 
    h =20m
11.  The spirit absorbs latent heat of vaporization from the palm to evaporate. This causes cooling in the palm as it evaporates( deny vaporizes)
12.     
    1. Reads a smaller value than the weight of the box( weightlessness)
       (reading reduces/ moves(deflects) to the left/ anticlockwise
    2. Reads the actual weight of the box/ reading remains constant/ nothing happens/ pointer remains stationary
    3. Reads a value bigger(greater/ higher) than the weight of the box./ Reading increases/ meter moves(deflects) to the right/ clockwise 
       (deny "mass of the box")
13. As it sinks, up thrust increases and stops when the upthrust is equal to the weight of the object/ density of object is half density of water - reject body displaces it's own weight on a fluid.

SECTION B

14.   
    1.    
       1.   
          • Weight  of the bucket/ force of gravity/ Gravitational force
          • Tension on the string 
            (reject symbol)
       2. Part of the centripetal force required is provided by the weight / both tension & weight act in the same direction therefore tension will be less.
       3.  
          • Water is likely to pour out
          • At a certain minimum speed, the centripetal force is less than what is required to keep the motion, therefore, some water spills out./ The body is moving at a speed less than the critical speed.
    2.   F= T = mv² 
                      r
       = 0.04 x 12 x12  
                    1
       =5.76N
15.    
    1.      
       1.  Upon sucking, the liquid flows in the delivery tube but stops on releasing because the sucking force is withdrawn/ Liquid flows because of the pressure difference
       2. The liquid fails to flow on release because there is no pressure difference to push the liquid up the tube without sucking/ the level of the container is above the liquid level.
    2. Upon squeezing the sides of the bottle, the pressure inside the bottle increases forcing more water to enter the test-tube. this increases the average density of the test tube and its contents hence it sinks./ upthrust decrease
    3.  P_max=  F     
                  A_min 
       =      188       =23, 500N/m² 
            0.1 x 0.08
       = 2.35N/cm² 
16.    
    1.  
       1.  
          1. By measuring the temperature of water since the temperature of air is equal to that of water.
          2. By measuring length of air column. Volume of air is proportional to the lenght since the cross-sectional area is uniform
       2. Keeping the tube(vertical) and open throughout the experiment.
       3.  
          • Obtain several values of volume V and Temperature T/ calculate several ratios of V
          • Plot a graph of volume against absolute temperature
          • A straight line through origin is obtained showing Charles' law is obeyed.
       4. Stirring water before taking and recording temperature and volume
    2.     V₁ =    V₂
          T₁        T₂
          V₂= 2V₁ 
       T₂ = 2V₁ (20 + 273) = 586K
               V₁  
       586 - 273 = 313ºC   
17.    
    1. 
       
    2.  
       1.  Effort = 2 x load distance
          = 2x2
          =4
          alternatively:
          V.R = Effort distance   
                    Load distance
          Effort distance = V.r x load distance
          = 2 x 2
          = 4
          ( showing working is a must)
       2. Work done 
          = F x D
          = 5 x 10 x 2
          = 100J
          ( accept NM)
       3.  PE = Work done
          = 100j 
          ( accept nm, te, worked out value)
          ( 5 x 10 x 2) = 100J  
    3.    
       1. Obtain the difference  between the initial reading of the balance and the final reading of the balance
          ( mass = initial reading of balances - final reading of balances)
       2. E = 500t/ Q= 500t/ W = 500t  - reject E= Pt
       3. Heat supplied = heat gained by steam
          500t = ML_v
          L_v = 500t Jkg^-1
                   m
          Pt = ML_v
          ( deny Q= ML_v, units are a must)   
18.  
    1. Matter is anything that occupies space and has mass.
    2. As the temperature increases, the molecules of the liquid gain more kinetic energy.( reject volume, mass or weight) It increases the speed of motion of the molecules hence they move faster, travel further and increase in intermolecular distance causing increase in volume.
    3.  
       1. To magnify/ enlarge the pollen grains for better visibility.
       2. They are observed to move in random motion
       3. They are being hit/ bombarded by the invisible water molecules which are in constant/ continuous random motion hence also move in random motion.
       4.    
          • Rate of random motion of the pollen grains increases
          • Increase in temperature of water increases the kinetic energy of water molecules, which move with a higher speed thus knocking/ bombarding the pollen grains which in turn move more/ vigorously/ faster.