Physics Questions and Answers - Form 2 Mid Term 2 2022

QUESTIONS

1.                    
   1. State Hooke’s law. (1mk)
   2. Three identical springs are arranged to support a 50N load as shown.
      
      Given that one such spring extends by 2cm when a load of 20N hangs on its lower end, determine total extension of the system. (3mks)
   3. Distinguish between ductile and brittle material. (2mks)
   4. State two factors on which spring constant of a spring depends on. (2mks)
2. An object of height 1cm is placed 5cm in front of a concave mirror of focal length 3 cm. By scale drawing, determine: position size and nature of image formed. (3mks)
3.                          
   1. Define centre of gravity of a body. (2mks)
   2. Use simple sketches to show the three state of equilibrium. Name the states. (3mks)
4.                              
   1. Distinguish between real and virtual image. (2mks)
   2. The graph shows the variation of 1/u and 1/v for an object. From the graph, find the focal length of the mirror used. (3mks)
      
5. State one advantage of an alkaline battery over a lead acid battery. (1mk)
6. Sketch the magnetic pattern around the following conductors. (2mks)
   
7. When mercury in a glass thermometer is used to measure the temperature of hot water, it is observed that mercury level first drops before beginning to rise. Explain (1mk)
8. A copper rod and a piece of wood of the same size were placed in contact by wrapping them with a piece of paper as shown below;
   
   A source of heat is moved to and fro and from across the paper; state the observations made and explain your observation. (2mks)
9. State two factors affecting the strength of an electromagnetic. (2mks)

MARKING SCHEME

1.                    
   1. State Hooke’s law. (1mk)
      Hooke's law, law of elasticity discovered by the English scientist Robert Hooke in 1660, which states that, for relatively small deformations of an object, the displacement or size of the deformation is directly proportional to the deforming force or load
   2. Three identical springs are arranged to support a 50N load as shown.
      
      Given that one such spring extends by 2cm when a load of 20N hangs on its lower end, determine total extension of the system. (3mks)
      20N = 2cm
      F = ke
      k = ^F/_e
      k = 20 ÷ ²/₁₀₀
      k = 20 × ¹⁰⁰/₂
      k = 1000 N/m
      
      Lower spring
      F = 50N
      e = ^F/_k = ⁵⁰/₁₀₀₀ = 0.05m
      
      Upper spring
      F= 50 + 1.5 +0.5 = 26 N
                   2
      e = ^F/_k 
      e= ²⁶/₁₀₀₀ = 0.026
      
      Total extension
      0.05 m + 0.026 = 0.076 m
      =7.6 cm
   3. Distinguish between ductile and brittle material. (2mks)
      The main difference between ductile and brittle materials is that ductile materials are able to be drawn out into thin wires whereas brittle materials are hard but liable to break easily.
   4. State two factors on which spring constant of a spring depends on. (2mks)
      The spring constant will depend on the stiffness of the spring material, the thickness of the wire from which the spring is wound and, the diameter of the turns of the coil, the number of turns per unit length and the overall length of the spring.
2. An object of height 1cm is placed 5cm in front of a concave mirror of focal length 3 cm. By scale drawing, determine: position, size and nature of image formed. (3mks)
   
   The position of the image is PA' = 7.5 cm
   The size of the image is A'B' = 1.5 cm
   The nature of the image is real, inverted and magnified.
3.                          
   1. Define centre of gravity of a body. (2mks)
      centre of gravity, in physics, an imaginary point in a body of matter where, for convenience in certain calculations, the total weight of the body may be thought to be concentrated.
   2. Use simple sketches to show the three state of equilibrium. Name the states. (3mks)
      
4.                              
   1. Distinguish between real and virtual image. (2mks)
      Real images are obtained using a converging lens or a concave mirror. The size of the real image depends upon the placement of the object. A virtual image is an upright image that is achieved where the rays seem to diverge. A virtual image is produced with the help of a diverging lens or a convex mirror.
   2. The graph shows the variation of 1/u and 1/v for an object. From the graph, find the focal length of the mirror used. (3mks)
      
      At ¹/_u intercept, ¹/_f = ¹/_v
      ¹/_f = ¹/_0.08
      f = 12.5 cm
      At ¹/_v intercept, ¹/_f = ¹/_u
      ¹/_f = ¹/_0.08
      f = 12.5 cm
      Average f = 12.5+12.5  = 12.5 cm        
                                  2
5. State one advantage of an alkaline battery over a lead acid battery. (1mk)
   - Compared with acid-based and lead-based counterparts, this battery has lesser environmental impact. It does not require any special disposal methods.
   - The compounds inside an alkaline battery do not pose serious health issues except from mild irritations
   - Safety is also another advantage of alkaline battery.
6. Sketch the magnetic pattern around the following conductors. (2mks)
   
   
7. When mercury in a glass thermometer is used to measure the temperature of hot water, it is observed that mercury level first drops before beginning to rise. Explain (1mk)
   Due to expansion of the glass, mercury first falls but later on rises due to larger. coefficient of expansion for mercury than that of glass.
8. A copper rod and a piece of wood of the same size were placed in contact by wrapping them with a piece of paper as shown below;
   
   A source of heat is moved to and fro and from across the paper; state the observations made and explain your observation. (2mks)
   The side of the paper around the wood burns first. This is because wood being a poor conductor of heat, does not allow the excess heat to pass through it so it gets charred.
   
9. State two factors affecting the strength of an electromagnetic. (2mks)
   The four main factors that affect the strength of an electromagnet are the loop count, the current, the wire size, and the presence of an iron core.