Physics Questions and Answers - Form 2 Mid Term 2 Exams 2021

INSTRUCTIONS TO CANDIDATES:

• This paper consists of sections: A and B
• Answer all the questions in section A and B
• All workings must be clearly shown.
• Mathematical tables and electronic calculators may be used.

SECTION A (25MARKS)
Answer all question this section

1. Distinguish between mass and weight of a body stating the SI units for each. (2mks) 
2. The figure below shows part of scale of vernier calipers.
   
   What is the reading indicated on the scale ________________(1mk)
3. 180cm³ of fresh water of density 100kg/m³ is mixed with 2200cm³ of sea water of density 1025kg/m³. Calculate the density of the mixture (4mks)
4. Explain why fish can survive under water when the surface is already frozen (2mks)
5. Two inflated balloons are at the same level while suspended from threads a short distance apart as shown below;
   
   Some air is blown gently in the space between the balloon in horizontal direction. Explain what happens to the balloons. (2mks)
6. State one advantage of an alkaline battery over a lead acid battery.  (1mk)
7. The diagram below shows a permanent magnet suspended by a spring. State with reason the behaviour of the magnet when the switch is closed.    (2mks)
   
8. Convection and diffusion both involve motion of fluids. Distinguish between the two.   (2mks)
9. A negatively, charged rod is brought close to (but not touching) an uncharged sphere. If the sphere is momentarily earthed and then the rod is removed, briefly explain what happens. (2mks)
10. Indicate on the diagram below, the level of mercury in the tubes X and Y  (2mks)
    
11. An object weighs 1200N on a certain planet. What is the gravitational field strength of this lanet if the object is 60kg?  (3mks)
12. State two properties of a thermometric liquid.  (2mks)

SECTION B (55MARKS)
Answer all question this section 13.

13.  
    1. Define pressure and give its S.I nits.  (2mks)
    2. The diagram below represents a motor car hydraulic braking system;
       
       
       1. State two properties of the liquid used as a brake fluid (2mks)
       2. Given that in the diagram (b) above the master piston has an area of 15cm² and the slave piston has an area of 50cm² a force of 100N is applied on the master piston. Find the force used to stop the car. (3mks)
    3. Compare the values of pressure in the two pistons above and give a reason for your answer.(2mks)
    4. Give a reason why gas is not suitable for use in place of the brake fluid.  (1mk)
    5. Xcm³ of substance A which has density of 800kg/m³ is mixed with 100cm of water with a density of 1000kg/m³. The density of the mixture is 960kg/m³. Determine the value of X (3mks)
14.  
    1. Give reasons why it is necessary to leave the caps of the cells open when charging an accumulator (1mk)
    2. Define current and state its SI unit (2mks)
    3. A charge of 120 coulombs flow through a 1 am every minute. Calculate the current flowing through the lamp  (3mks)
    4. What do you understand by open and closed circuits.  ( 2mks)
    5.  
       1. State the basic law of electrostatics  (1mk)
       2. Explain how you would use an electroscope to distinguish between a conductor and an insulator   (3mks)
15.  
    1. The figure shows an arrangement of source of light, an opaque object and a screen. Using A, B and C as point sources, sketch on the same diagram labeled a ray diagram to show what is observed on the screen. (3mks)
       
    2. In a certain pinhole camera, the screen is 10cm from the pinhole. When the pinhole is placed 6cm away from a tree, a sharp image of a tree 16cm high is formed on the screen. Find the height of the tree. ( 3mks)
    3. Distinguish between Lunar and Solar eclipse by stating the events that lead to the formation of each (4mks)
    4. A girl stands 4 m in front of a plane mirror
       1. What is the distance between the girl and the mirror (3mks)
       2. Explain how you would use an electroscope to distinguish between a conductor and an insulator  (3mks)
16.  
    1. Fill in the table of charges appropriately             ( 5mks)
       

       Charge on Electroscope	Charge brought near cap	Effects on leaf divergence
       +  −	+  −
       + or −	Uncharged body

    2. What is the name given to the method of charging an electroscope where it requires an opposite charge to the one of the charging materials?  (1mk)
    3. Distinguish between a basic physical quantity and a derived physical quantity giving an example of each.   (3mks)
    4. State any two ways by which frictional force between two surfaces can be reduced.  (1mk)
    5. Explain why large mercury drops form oral ball on a glass slide (2mks)
    6. Explain why am man using a parachute falls through air slowly while a stone falls through air very fast  (2mks)

MARKING SCHEME

1. Mass is the quantity of matter in a body while weight is the measure of the pull of gravity on the body. weight S.I unit Newtons (N) (½mk)
   mass SI unit Kilogram(kg) (½mk)
2. Main scale reading = 7.4cm
   Vernier scale reading = 4x0.01 = 0.04cm
   Total reading = 7.4 +0.04 = 7.44 cm (1mk)
3. Density of mixture = mass of mixture  
                                 Volume of mixture
   Mass of fresh water = 1800 x 1 =1800g
   Mass of sea water = 2200 x 1.025 = 2255g
   Density of mixture = 2255 +1800
                                  1800 + 2200
                               = 1.01375g/cm³
4. Ice being less dense than water, floats on water. Water at 4°C being the most dense, remains at the bottom of the lake and aquatic life survives.
5. The two balloons move towards each other. On blowing air between the balloons, the speed of air increases and pressure reduces. The high atmospheric pressure on the sides pushes the balloons towards each other.
6. Large currents can be drawn from them
   They can be kept in a discharged condition for a very long time before the cells are ruined
   They require very little attention to maintain
   They are lighter (portable) than lead-acid accumulators
7. The magnet towards on passing the current on the coil, the core XY is magnetized with the South
   Pole on Y thus attracting the North Pole of the permanent magnet.
8. Convection is the transfer of heat through fluids
   Diffusion is the process by which particles spread from regions of high concentration to those of low concentration
9. The sphere acquires a positive charge by induction method.
   
10.  
    
11. w=Mg
    1200 = 60xg
    g= 1200 = 20N/Kg
           60
12.  
    • Easily visible
    • Expand or contract uniformly
    • Have a wide range of temperature
    • Not stick to the walls of the glass

13.  
    1. Pressure is force per unit area S.I unit is N/m? or Pascal's.
    2.  
       1.  
          • incompressible
          • Low freezing point
          • High boiling point
          • Should not corrode the parts of the brake system
       2. P_A=P_a
          F₁=F₂
          A₁ A₂
          100 =  F₂
           15     50
          F2 = 333.3 N
    3. P_A= P_B
       Pressure in liquids is transmitted equally in all directions.
    4. Gas is compressible in liquid is incompressible.
    5. Total mass = m₁ + m₂
       m₁ = 0.8 x x =0.8x g
       m₂= 1x100 = 100g
       total = (0.8x + 1000)g
       total volume = (x +100) = 0.96
                               x+100
       x  =   4     
              0.16
           = 25cm³   
14.  
    1. Give reasons why it is necessary to leave the caps of the cells open when charging an accumulator   ( 1mk)
       • For free circulation of air i.e allow Hydrogen to escape.
    2. Define current and state its SI unit   (2mks)
       • is rate flow of charge in a circuit. SI unit is Amperes
    3. A charge of 120 coulombs flow through a 1 am every minute. Calculate the current flowing through th lamp. (3mks)
       I= Q  = 120 = 2A
       t            60
    4. What do you understand by open and closed circuits?   ( 2mks)
       • open-no current flows
       • closed - current flows
    5.  
       1. Like charges repel while unlike charges attract.
       2.  
          • Charge the electroscope
          • Touch the cap using the materials
          • In case of collapsing of leaf then the material is a conductor but in case of remaining the same then the material is an insulator.
15.  
    1. The figure shows an arrangement of source of light, an opaque object and a screen. Using A.B and C as point sources, sketch on the same diagram labeled a ray diagram to show what is observed on the screen.
       
    2. In a certain pinhole camera, the screen is 10cm from the pinhole. When the pinhole is placed 6cm away from a tree, a sharp image of a tree 16cm high is formed on the screen. Find the height of the tree. ( 3mks)
       hi  = v
       ho     u
       1.6 = 10cm
        hо       бсm
       ho = 6 × 16
                 10                =9.6cm
    3.  
       1. Lunar
          
          • Earth in between the sun and the moon
          • Earth shadow is focused on the moon
       2. Solar
          • moon in between the Earth and the moon
          • moon shadow is focused on the Earth
          • occur during new moon.
    4. A girl stands 4m in front of a plane mirror
       1. What is the distance between the girl and her image?
          2x4 = 8m
       2. Explain how you would use an electroscope to distinguish between a conductor and an insulator    ( 3mks)
          charge the electroscope touch the cap using the materials in case of collapsing of leaf then the material is a conductor but in case of remaining the same then the material is an insulator.
16.  
    1. Fill in the table of charges appropriately    ( 5mks)
       

       Charge on Electroscope	Charge brought near cap	Effects on leaf divergence
       +  −	+  −	Divergence increase        "         decrease
       + or −	Uncharged body	No effect

    2. What is the name given to the method of charging an electroscope where it requires an opposite charge to the one of the charging materials?
       • By induction
    3. 
       

       Basic physical quantity	Derived physical quantity
       -quantities that cannot be obtained from any other physical quantity e.g. length, mass, time,  electric current e.t.c	-quantities that can be obtained by multiplication or division of basic physical quantities e.g. area, volume and density

        (3mks)
    4.  
       • oiling
       • greasing
       • using rollers
       • smoothening
    5. This is because cohesive forces between mercury molecules are stronger than adhesive force between molecules of mercury and glass (2mks)
    6. This is because a parachute encounters higher resistance as it tails through the air due to large size while a stone experience less resistance due to its small size (2mks)