## QUESTIONS

SECTION A;30MKS 1. Explain why repulsion between magnets is the surest way of confirming the polarity of a magnet. (2mks).
2. In an experiment, a student obtained the thickness of an object as 6.40mm.
1. state the accuracy of the instrument used.(1mk)
2. Write the measurement in SI Units (1mk).
3. If the measuring instrument had a zero error of +0.02mm, determine the actual thickness of the object. (2mks).
3. A bus that carries goods in the under seats carrier is more stable than one that carries goods in the carrier at the top. Explain this observation. (2mks).
4. The figure below shows a uniform wooden plank which weighs 10N. The plank is balanced at 0.8m from one end by a mass of 2.5kg. Determine the length of the wooden plank in metres. (4mks).
5.
1. Complete the diagram below to show the position of the image. (3mks). 2. Give TWO applications of the set-up shown above. (2mks).
6. Give a reason why heat transfer by Radiation is faster than heat transfer by Conduction. (2mks).
7. State THREE factors on which the rate of heat flow depends on. (3mks).
8. Liquids expand when heated and contract when cooled. However this is not always true for water.
1. what name is given to the behavior of water? (1mk).
2. State TWO importance of this behavior of water. (2mks).
3. State any TWO disadvantages of this behavior. (2mks).
9. The figure below shows poles of two bar magnets placed close to one another. Complete the diagrams to show the magnetic field patterns between the two magnets.(2mks). 10. State why convex mirrors are used for rear view mirror in vehicles.(1mk).

SECTION B;40MKS

1. In an oil-drop experiment, an olive oil drop of diameter 0.7mm was carefully put on lycopodium powder which had been sprinkled on a calm water surface. The oil drop spread out into a roughly circular patch of diameter 73.5cm on the water surface.
1. Describe how the oil drop spreads out to form an oil patch. (2mks).
2. What is the role of the Lycopodium powder. (1mk).
3. Calculate the volume of the oil drop in mm3. (3mks).
4. Determine the expression for the area of the oil patch in mm3. (2mks).
5. Determine the thickness of the olive oil molecule and express your answer in standard form. (3mks).
6. State TWO assumptions that you have made in this expt. (2mks).
2.
1. State TWO methods of magnetization. (2mks).
2. Complete the diagram below to show the magnetic field patterns. (2mks). 3.
1. The figure below shows a U-shaped iron core. Indicate the polarity marked X and Y. X-
Y-
2. State TWO applications of such an electro-magnet. (2mks).
3. State two modifications that can be made to the set up above in order to demagnetize the iron core (2mks)
3.
1. The figure below shows a graph of 1/V against 1/U for a concave mirror. Use the graph to determine the focal length of the mirror. (3mks) 2. Determine the image distance V when the magnification m=2 for the concave mirror above. (3mks)
3.
1. A small object is placed 15cm in front of a convex mirror of focal length 10cm. Determine the position of the image. (3mks)
2. Give TWO characteristics of the image formed in part c(i) above. (2mks)
4. The table below shows the two major defects of the simple cell. Complete the table by stating the effects and remedies of these defects. (4mks)
 DEFECT EFFECT REMEDY Polarisation Local action
5. Define the following terms;
1. Centre of gravity (C.O.G) (1mk)
2. Stable equilibrium. (1mk)

## MARKING SCHEME SECTION A;30MKS

1. Explain why repulsion between magnets is the surest way of confirming the polarity of a magnet. (2mks).
• Attraction can take place between a magnet and any magnetic material but repulsion occurs only between hike poles.
2. In an experiment, a student obtained the thickness of an object as 6.40mm.
1. state the accuracy of the instrument used.(1mk)
• 2d.p. or 0.01mm
2. Write the measurement in SI Units (1mk).
• 6.40/1000= 0.00640
=6.40*10-3 m
3. If the measuring instrument had a zero error of +0.02mm, determine the actual thickness of the object. (2mks).
• 6.40mm- 0.02mm=6.38mm
3. A bus that carries goods in the under seats carrier is more stable than one that carries goods in the carrier at the top. Explain this observation. (2mks).
• Goods under the seat lowers the c.o.g. making the bus more stable
• Goods on the top of the bus rises the c.o.g. making the bus less stable.
4. The figure below shows a uniform wooden plank which weighs 10N. The plank is balanced at 0.8m from one end by a mass of 2.5kg.

Determine the length of the wooden plank in metres. (4mks).
• F1D1=F2D2
10*X= 25*0.8
X=(25*0.8)/10
5.
1. Complete the diagram below to show the position of the image. (3mks).
2. Give TWO applications of the set-up shown above. (2mks).
• Shaving mirror
• Dentist mirror
6. Give a reason why heat transfer by Radiation is faster than heat transfer by Conduction. (2mks).
• Radiation travels at the speed of light since it is an electromagnetic wave while conduction involves vibration of particles.
7. State THREE factors on which the rate of heat flow depends on. (3mks).
• The length of the conductor
• The x-sectional area of the conductor
• The nature of the material making the conductor
8. Liquids expand when heated and contract when cooled. However this is not always true for water.
1. what name is given to the behavior of water? (1mk).
• The anomalous expansion of water
2. State TWO importance of this behavior of water. (2mks).
• Facilitates the survival of aquatic animals during winter.
• Withering of rocks
3. State any TWO disadvantages of this behavior. (2mks).
• Formation of ice-bergs
• Bursting of water pipes.
9. The figure below shows poles of two bar magnets placed close to one another. Complete the diagrams to show the magnetic field patterns between the two magnets.(2mks).
10. State why convex mirrors are used for rear view mirror in vehicles.(1mk).
• They have a wide field of views.
11. In an oil-drop experiment, an olive oil drop of diameter 0.7mm was carefully put on lycopodium powder which had been sprinkled on a calm water surface. The oil drop spread out into a roughly circular patch of diameter 73.5cm on the water surface.
1. Describe how the oil drop spreads out to form an oil patch. (2mks).
• The oil spreads over the water due to reduced surface tension such that the adhensive forces between the oil particles is than the cohesive forces between water molecules
2. What is the role of the Lycopodium powder. (1mk).
• It lowers the surface tension of water
• It marks the boundary of the oil particle spread.
3. Calculate the volume of the oil drop in mm3. (3mks).
• V=4/3Ïr3=4/3Ã(3.5Ã10-4)3 Ã Ï =1.80 Ã10-10 m3
4. Determine the expression for the area of the oil patch in mm3. (2mks).
• V=Ïr2h=ÏÃ(0.3675)2Ãh=0.42h
5. Determine the thickness of the olive oil molecule and express your answer in standard form. (3mks).
• Vdrop= VPATCH=(1.80Ã10-10)Ã·0.42=h= 4.29Ã10-10 m
6. State TWO assumptions that you have made in this expt. (2mks).
• The volume of oil drop is equal to volume of oil patch
• The oil patch spreads to form a monolayer
12.
1. State TWO methods of magnetization. (2mks).
• Electrical method
• Induction
• stroking
2. Complete the diagram below to show the magnetic field patterns. (2mks).
3.
1. The figure below shows a U-shaped iron core. Indicate the polarity marked X and Y.
X- North
Y- South
2. State TWO applications of such an electro-magnet. (2mks).
• Making electro-magnet bells
• Making fire alarms
3. State two modifications that can be made to the set up above in order to demagnetize the iron core (2mks)
• Using a.c. instead of d.d.
• Positioning the set ip in a west-east direction rather than north-south
13.
1. The figure below shows a graph of 1/V against 1/U for a concave mirror. Use the graph to determine the focal length of the mirror. (3mks)
• 1/f=1/v+1/u
• X=1/f=1/v=1/10 f=10cm
• At Y 1/f=1/u=1/10 f=10cm
2. Determine the image distance V when the magnification m=2 for the concave mirror above. (3mks)
• m=v/f-1
2=v/10-1
V=(3)(10)
30cm
3.
1. A small object is placed 15cm in front of a convex mirror of focal length 10cm. Determine the position of the image. (3mks)
• u=15cm 1/f=1/v+1/u
f=10cm 1/v=1/f-1/u=1/10-1/15=1/30 v= 30
2. Give TWO characteristics of the image formed in part c(i) above. (2mks)
• It is real
• It is inverted
• It is magnified
• Formed same side as object
14. The table below shows the two major defects of the simple cell. Complete the table by stating the effects and remedies of these defects. (4mks)
 DEFECT EFFECT REMEDY Polarisation Bubbles of hydrogen accumulate on the copper plate Brushing away of Putting in a depolarizer/oxidizing agent.bubbles Local action Corrosion of the zinc plate by the acid Amalgamation with mercury layerUsing pure zinc
15. Define the following terms;
1. Centre of gravity (C.O.G) (1mk)
• This is the point at which the weight of an object is positioned.
2. Stable equilibrium. (1mk)
• It is a position where the line through c.o.g. to the base is always passing via the base and toppling is not possible