SUKELLEMO JOINT MOCK
Kenya Certificate of Secondary Education
PHYSICS PAPER 1
2 hours
Instructions to Candidates
 Answer all the questions in the spaces provided.
 This paper consists of 2 sections: Section A and B
 All working must be clearly shown.
 Nonprogrammable silent electronic calculators and KNEC mathematical tables may be used.
SECTION A (25 MARKS)
Answer ALL the questions in this section in the spaces provided
 The level of water in a burette is at 30 cm^{3}. 400 drops of water each of volume 0.015 cm^{3} was removed from the burette.
Determine the new level of water in the burette [3 mks]  Calculate the temperature change of water as it falls through a height of 20 m. (Take g = 10 N/kg and s.h.c of water =4200 J/kg/K) [3 mks]
 State the SI unit of density [1 mk]
 Give a reason why heat transfer by radiation is faster than heat transfer by conduction [1 mk]
 A railway truck of mass 4000 kg moving at 3 m/s collides with a stationary truck of mass 2000 kg. The couplings join and the trucks move off together. Calculate their common velocity after collision. [3 mks]
 State the principle of moments [1 mk]
 An air bubble with a volume of 1 cm^{3} escapes from the helmet of a diver at a depth of 200 m below the water surface. What will be the volume of the bubble immediately it breaks the surface of water? (Take atmospheric pressure = 10 m of water) [4 mks]
 Calculate the acceleration due to gravity on a planet where an object released from rest falls through a height of 54.2 m in 1.08 s. [3 mks]
 State the three factors on which the rate of heat flow depends on. [3 mks]
 Under a driving force of 3000 N, a car of mass 1200 kg has an acceleration of 1.3 m/s^{2}. Find the frictional resistance acting in the car. [3 mks]
SECTION B (55 MARKS)
Answer ALL the questions in this section

 Explain the following as regards the solar heater:
 Why the pipe is fixed to a darkcoloured collector plate. [1 mk]
 Why the pipe is made of copper [1 mk]
 Why the pipe is coiled several times [1 mk]
 Why the collector plate is fixed to an insulator. [1 mk]
 Why the panel front is covered with glass. [1 mk]
 Liquids expand when heated and contract when cooled. However this is not always true for water.
 What name is given to the behavior of water? [1 mk]
 States two importance of this behavior of water. [2 mks]
 State any two disadvantages of this behavior. [2 mk]
 A man wants to fit a brass ring onto a steel rod of diameter equal to the inner diameter of the ring. Explain how this can be achieved [2 mk]
 Explain the following as regards the solar heater:
 The figure below shows a hydraulic press supporting a load F.
 What properties of liquids make them suitable for use in hydraulic machines such as the one above? [2 mks]
 If A and a are areas of crosssection of the pistons, and the lengths of the arm are as given, find:
 The force Fo [3 mks]
 The mechanical advantage [1 mks]
 The efficiency of the machine [3 mks]
 State two reasons why the efficiency of a pulley system is always less than 100% [2 mks]

 You are provided with the following:
 A block of wood
 A spring balance
 Thin thread
 Overflow can
 A small measuring cylinder
 Some liquid
With the aid of a labeled diagram an experiment to the law of floatation
 The diagram below shows a car acid hydrometer.
 Indicate on the diagram above the minimum and the maximum measurement to be taken. [2 mks]
 State the reason why the bulb is wide. [2 mks]

 Figure below shows a uniform plank of weight 20N and length 1.0m balanced by a 0.5kg mass at a distance x from the pivot point O.
Determine the value of X [2 mks]  When the block is completely immersed in water the pivot O must shift by 0.05 m to the left for the system to balance. The density of water is 1000 kgm3.Determine:
 The upthrust U on the block. [3 mks]
 The volume of the block. [2 mks]
 Figure below shows a uniform plank of weight 20N and length 1.0m balanced by a 0.5kg mass at a distance x from the pivot point O.
 You are provided with the following:


 Distinguish between elastic and inelastic collisions. [2 mks]
 A body of mass 5 kg is ejected vertically to a height of 7.2 m from the ground when a force acts on it for 0.1s. Calculate the force used to eject the body.[3mks]
 Explain why the moon is said to be accelerating when revolving around the earth at constant speed [2mks]
 A stone is whirled in a vertical circle as shown in the figure below using a string of length 40 cm. A, B, C and D are various positions of the stone in its motion. The stone makes 2 revolutions per second and has a mass of 100g.
 Calculate:
 The angular velocity [ 3mks]
 The tension on the string at position A [3 mks]
 At C where the stone has acquired a constant angular speed, the string cuts. The stone takes 0.5 seconds to land on the ground. How high is point C above the ground. [2 mks]
 How far does it travel horizontally before hitting the ground. [2 mks]
 Calculate:

MARKING SCHEME
SECTION A (25 MARKS)
Answer ALL the questions in this section in the spaces provided
 The level of water in a burette is at 30 cm^{3}. 400 drops of water each of volume 0.015 cm^{3} was removed from the burette.
 Volume of drops =(400 x 0.015)cm^{3} = 6cm^{3}
Determine the new level of water in the burette [3 mks]  New level = (30+6)=36cm^{3}
 Volume of drops =(400 x 0.015)cm^{3} = 6cm^{3}
 Calculate the temperature change of water as it falls through a height of 20 m. (Take g = 10 N/kg and s.h.c of water =4200 J/kg/K) [3 mks]
 G.P.E = Heat again
Mwgh = MwCwΔθ
10 x 20 = 4200Δθ
Temperature change Δθ = 0.0476ºC
 G.P.E = Heat again
 State the SI unit of density [1 mk]
 Kilograms per cubic metre
 Kilograms per cubic metre
 Give a reason why heat transfer by radiation is faster than heat transfer by conduction [1 mk]
 Radiation is propagated by means of e.m waves while conduction involves movement of particles which are prone to distraction through collisions.
 Radiation is propagated by means of e.m waves while conduction involves movement of particles which are prone to distraction through collisions.
 A railway truck of mass 4000 kg moving at 3 m/s collides with a stationary truck of mass 2000 kg. The couplings join and the trucks move off together. Calculate their common velocity after collision. [3 mks]
 m_{1}u_{1} + m_{2}u_{2} =(m_{1} + m_{2})
4000 x 3 + 0= 6000v
v= 2m/s
 m_{1}u_{1} + m_{2}u_{2} =(m_{1} + m_{2})
 State the principle of moments [1 mk]
 Sum of clockwise moments about a point is equal to the sum of anticlockwise moments about the same point.
 Sum of clockwise moments about a point is equal to the sum of anticlockwise moments about the same point.
 An air bubble with a volume of 1 cm^{3} escapes from the helmet of a diver at a depth of 200 m below the water surface. What will be the volume of the bubble immediately it breaks the surface of water? (Take atmospheric pressure = 10 m of water) [4 mks]
 P_{1}V_{1} = P_{2}V_{2}
P_{1} = (200 +10)m
V_{1} = 1cm^{3}
P_{2} = 10m
v_{2} = ?
210m x 1cm^{3} = 10m x V_{2}
v_{2} = ^{210}/_{10}
=21cm^{3}
 P_{1}V_{1} = P_{2}V_{2}
 Calculate the acceleration due to gravity on a planet where an object released from rest falls through a height of 54.2 m in 1.08 s. [3 mks]
 s= ut + ^{1}/_{2 }gt^{2}
54.2 = 0 +^{1}/_{2 }g x 1.08^{2}
g= 92.94m/s^{2}
 s= ut + ^{1}/_{2 }gt^{2}
 State the three factors on which the rate of heat flow depends on. [3 mks]
 Length of the conductor
 The cross section area of the conductor
 The material of the conductor
 Temperature difference of the ends of a conductor
 Under a driving force of 3000 N, a car of mass 1200 kg has an acceleration of 1.3 m/s^{2}. Find the frictional resistance acting in the car. [3 mks]
 F=ma
1200 x 1.3
F= 1560N
F = 3000 1560
1440N
 F=ma
SECTION B (55 MARKS)
Answer ALL the questions in this section

 Explain the following as regards the solar heater:
 Why the pipe is fixed to a darkcoloured collector plate. [1 mk]
 To get heated faster since dark is a good absorber and emitter
 To get heated faster since dark is a good absorber and emitter
 Why the pipe is made of copper [1 mk]
 To conduct heat needed for heating water.
 To conduct heat needed for heating water.
 Why the pipe is coiled several times [1 mk]
 To increase the surface area for heating
 To increase the surface area for heating
 Why the collector plate is fixed to an insulator. [1 mk]
 To minimize heat losses to the environment
 To minimize heat losses to the environment
 Why the panel front is covered with glass. [1 mk]
 To prevent escape of the reflected radiant heat which has a longer wavelength
 To prevent escape of the reflected radiant heat which has a longer wavelength
 Why the pipe is fixed to a darkcoloured collector plate. [1 mk]
 Liquids expand when heated and contract when cooled. However this is not always true for water.
 What name is given to the behavior of water? [1 mk]
 Anomolous expansion of water.
 Anomolous expansion of water.
 States two importance of this behavior of water. [2 mks]
 Enables the survival of aquatic during winters
 Enables weathering of rocks to take place.
 State any two disadvantages of this behavior. [2 mk]
 Can cause accidents in water transportation
 Can cause pipe bursts
 A man wants to fit a brass ring onto a steel rod of diameter equal to the inner diameter of the ring. Explain how this can be achieved [2 mk]
 Heat the ring to allow its diameter increase. Fix the rod into the hole and allow the two to cool.
 Heat the ring to allow its diameter increase. Fix the rod into the hole and allow the two to cool.
 What name is given to the behavior of water? [1 mk]
 Explain the following as regards the solar heater:
 The figure below shows a hydraulic press supporting a load F.
 What properties of liquids make them suitable for use in hydraulic machines such as the one above? [2 mks]
 Incompressible
 Nonerrosive
 If A and a are areas of crosssection of the pistons, and the lengths of the arm are as given, find:
 The force F_{a} [3 mks]
 ^{Fa}/_{0.01} = ^{700}/_{0.2}
 F_{a} = 35N
F_{o} x 1 = F_{a} x 0.2
F_{o} = 35 x 0.2
=7N
 The mechanical advantage [1 mks]
 M.A = ^{L}/_{E}
 ^{700}/_{7}
 M.A = 100
 The efficiency of the machine [3 mks]
 VR = V.Rl x VRh
^{0.2}/_{0.01} x ^{1}/_{0.2}
V.R = 100  ^{M.A}/_{V.R} x 100%
 ^{100}/_{100} x 100%
 VR = V.Rl x VRh
 State two reasons why the efficiency of a pulley system is always less than 100% [2 mks]
 Part of the applied effort is raising the blocks
 Some energy is overcoming friction between the moveable parts
 The force F_{a} [3 mks]
 What properties of liquids make them suitable for use in hydraulic machines such as the one above? [2 mks]

 You are provided with the following:
 A block of wood
 A spring balance
 Thin thread
 Overflow can
 A small measuring cylinder
 Some liquid
With the aid of a labeled diagram an experiment to the law of floatation
 Measure the weight of blocks of wood in air
 Fill the overflow can with the liquid and let the excess liquid flow out then place an empty measuring cylinder below the spout
 Place the block of wood in the overflow can and measure the volume of the displaced liquid inside the cylinder
 Using the density of the liquid, calculate the mass and then weight of the displaced liquid
 Compare the weight of the block with the value of the weight of the displaced liquid
 The diagram below shows a car acid hydrometer.
 Indicate on the diagram above the minimum and the maximum measurement to be taken. [2 mks]
 Q minimum
 P maximum
 State the reason why the bulb is wide. [2 mks]
 To displace the large volume of liquid to provide sufficient upthrust necessary for floating.
 Indicate on the diagram above the minimum and the maximum measurement to be taken. [2 mks]

 Figure below shows a uniform plank of weight 20N and length 1.0m balanced by a 0.5kg mass at a distance x from the pivot point O.
Determine the value of X [2 mks] 20(0.5 x) = 5x
x = 0.4m
 20(0.5 x) = 5x
 When the block is completely immersed in water the pivot O must shift by 0.05 m to the left for the system to balance. The density of water is 1000 kgm^{3}Determine:
 The upthrust U on the block. [3 mks]
 F x 0.45= 20 x 0.05
F = 2.222  U = 5  2.222
U = 2.778N
 F x 0.45= 20 x 0.05
 The volume of the block. [2 mks]
 U = pVg
1000 x 10 x v = 2.778
V= 2.778 x 10^{4}m^{3}
 U = pVg
 The upthrust U on the block. [3 mks]
 Figure below shows a uniform plank of weight 20N and length 1.0m balanced by a 0.5kg mass at a distance x from the pivot point O.
 You are provided with the following:


 Distinguish between elastic and inelastic collisions. [2 mks]
 For elastic collision, both K.E and momentum are conserved while for inelastic collision only momentum is conserved.
 For elastic collision, both K.E and momentum are conserved while for inelastic collision only momentum is conserved.
 A body of mass 5 kg is ejected vertically to a height of 7.2 m from the ground when a force acts on it for 0.1s. Calculate the force used to eject the body.[3mks]
 v^{2} = u^{2}  2gs
0= u^{2}  2 x 10 x 7.2
u= 12m/s
v=0  Ft = momentum
F= ^{5 x 12}/_{0.1}
=600N
 v^{2} = u^{2}  2gs
 Distinguish between elastic and inelastic collisions. [2 mks]
 Explain why the moon is said to be accelerating when revolving around the earth at constant speed [2mks]
 Because instantenous change in velocity in terms of direction
 Because instantenous change in velocity in terms of direction
 A stone is whirled in a vertical circle as shown in the figure below using a string of length 40 cm. A, B, C and D are various positions of the stone in its motion. The stone makes 2 revolutions per second and has a mass of 100g.
 Calculate:
 The angular velocity [ 3mks]
 w = 2πf
 2 x 3.142 x 2
 12.568 rads^{1}
 The tension on the string at position A [3 mks]
 T_{A} = mrw^{2} = mg
 0.1 x 0.4 x 12.568^{2}  0.1 x 10
 T_{A} = 5.318N
 The angular velocity [ 3mks]
 At C where the stone has acquired a constant angular speed, the string cuts. The stone takes 0.5 seconds to land on the ground. How high is point C above the ground. [2 mks]
 h = 1/2gt^{2}
0.5 x 10 x 0.5^{2}
h= 1.25m
 h = 1/2gt^{2}
 How far does it travel horizontally before hitting the ground. [2 mks]
 v=wr
12.568 x 0.4
5.027m/s  R = ut
5.027 x 0.5
2.514m
 v=wr
 Calculate:

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