Free KCSE Physics Topical Questions KNEC Standards

K.C.S.E Physics Q & A - MODEL 2019PP2QN19

15/10/2020

K.C.S.E Physics Q & A - MODEL 2019PP2QN19

(a) Define half life as used in radioactivity.
(b) Figure 13 shows a device used to detect radioactivity by forming tracks when air is ionised.

(i) State the name of the device shown.
(ii) State how air in the device gets ionised.
(iii) Describe how tracks are formed
(c) (i) State two factors that determine the speed of the photoelectrons emitted from a metal surface
(ii) The energy of a photon of light is 2.21 eV. (electronic charge is 1.6x10^-19C and planks constant h is 6.63x10^-34Js)
I. Express this energy in joules.
II. Determine the frequency of the light that produces the photon.

answers

(a) Half life is the time taken for half the number of nuclides initially present in a sample to decay
(b). (ii) Expansion closed chamber
(ii) Due to collisions between the molecules from the radiations source and the air molecules
(iii) When the piston is pulled down air expands hence cools.
(c)(i) The work function of the metal
Energy of incident radiation frequency/wavelength

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K.C.S.E Physics Q & A - MODEL 2019PP1QN18

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN18

(a) Figure 9 shows a graph of pressure against temperature for a fixed mass of gas at constant volume.

From the graph, determine the values of n arid e given that P = nT + c where n and c are constants.
(b) Explain why it is not possible to obtain zero pressure of a gas in real life situation.
(c) A fixed mass of a gas occupies 1.5 X 10^-3 m^-3 at a pressure of 760 mmHg and a temperature of 273 K. Determine the volume the gas will occupy at a temperature of 290K and a pressure of 720 mmHg.
(d) State any three assumptions made in kinetic theory of gases.

answers

(b) It is not possible to reduce the pressure of a gas to zero since by then most of the temperatures are very low hence the gas liquefies.

(d) Assumptions of the kinetic theory of gases:
Attraction of between the molecules is negligible.
Volume of the molecule is negligible compared to the volume of the container occupied by the gas.
The molecules undergo elastic collisions.
The length of time of a collision is negligible compared to the time between collisions.

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K.C.S.E Physics Q & A - MODEL 2019PP1QN17

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN17

(a) State what ¡s meant by Brownian Motion.
(b) Figure 8 shows the graph of velocity against time For a small steel ball Falling in a viscous liquid.

(a) State what ¡s meant by Brownian Motion. (1 mark) (b) Figure 8 shows the graph of velocity against time For a small steel ball Falling in a viscous liquid. (i) Describe the motion of the steel ball as represented by part OA (ii) Explain why the velocity of A and B is constant (c)A student throws a tennis ball vertically upwards from the ground and it lands back after 8 seconds.( acceleration due to gravity g =10ms-2) Determine the: (i) maximum height reached by the ball iii) velocity with which the ball hits the ground. (3 marks)

(i) Describe the motion of the steel ball as represented by part OA
(ii) Explain why the velocity of A and B is constant
(c)A student throws a tennis ball vertically upwards from the ground and it lands back after 8 seconds.( acceleration due to gravity g =10m/s2)
Determine the:
(i) maximum height reached by the ball
iii) velocity with which the ball hits the ground.

answers

(a) Continuous random motion of particles.
(b) (i) It accelerates, velocity increases.
(ii) As the ball falls through the fluid, the Viscous drag increases until the sum of the Viscous drag and the upthrust becomes equal the weight of the steel ball, hence the resultant force becomes zero.

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K.C.S.E Physics Q & A - MODEL 2019PP1QN16

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN16

(a) State the meaning of the term “heat capacity.”
(b) State how pressure affects the melting point of a substance.
(c)Figure 7 shows a set tip of apparatus that may be used to apparatus the specific latent heat of vaporization of steam

(I) Describe how the mass of condensed steam is determined.
(ii) Other than mass and time, state two other measurements that should be taken during the experiment.
(iii) Show how the measurements in (c)(ii) can be used to determine the specific latent heat of vaporization of water.
(iv) State the precaution that should be taken so that the mass of the condensed steam measured corresponds to the actual mass of steam collected during the time recorded in the experiment
(v) State why it is not necessary to measure temperature in in the set up

answers

(a) Heat capacity is the quantity of heat energy required to raise the temperature of a substance by 1K.
(b) - Increase in pressure lowers the melting point while decrease in (1 mark) pressure raises/increases the melting point.
(c) (i) - Measure the mass of the empty beaker M1.
Measure the mass of the beaker plus the condensed steam M2
Get the difference between the two masses (M2 —M1) = M
(ii) - Voltage
Current

(iv) - Start timing when the steam drops start forming out steadily and Stop immediately the beaker is withdrawn.
(V) Steam is produced at boiling point where temperature is constant.

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K.C.S.E Physics Q & A - MODEL 2019PP1QN15

31/7/2020

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K.C.S.E Physics Q & A - MODEL 2019PP1QN15

(a)Figure 6 shows n bottle top opener being used to open a bottle.

Indicate on the diagram the direction of the load and the effort.
(b) State two ways ¡n which an inclined plane can be made to reduce the applied effort when pulling a Load along the plane.
(c) A block and tackle system has three pulleys in the upper fixed block and two pulleys in the lower movable block.
(i) Draw a diagram to show how the system can be set up in order to lift a load arid indicate the position of the load and effort.
(ii) State the velocity ratio of the set up.
(iii) In such a block and tackle system an effort of 200N is required to lift a load of 600N. Determine its efficiency

answers

(b)Reducing the angle of inclination.
Reducing the friction — using rollers, lubricants etc.

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FORM I - PHYSICS SYLLABUS

Introduction to Physics (4 Lessons)
Measurements 1 (12 Lessons)
Force (16 Lessons)
Pressure (24 Lessons)
Particulate Nature of Matter (12 Lessons)
Thermal Expansion (12 Lessons)
Heat Transfer
Rectilinear Propagation of Light and Reflection at Plane Surface (16 Lessons)
Electrostatics (12 Lessons)
Cells and Simple Circuits (12 Lessons)

FORM II - PHYSICS SYLLABUS

Magnetism (12 Lessons)
Measurements II (16 Lessons)
Turning Effect of Force (10 Lessons)
Equilibrium Centre of Gravity (12 Lessons)
Reflection at Curved Surfaces (16 Lessons)
Magnetic Effect of Electric Current (18 Lessons)
Hooke's Law (8 Lessons)
Waves (14 Lessons)
Sound (12 Lessons)
Fluid Flow (14 Lessons)

FORM III - PHYSICS SYLLABUS

Linear Motion (20 Lessons)
Refraction of Light (20 Lessons)
Laws of Motion (15 Lessons)
Energy, Power and Machines (20 Lessons)
Current Electricity (20 Lessons)
Waves II(10 Lessons)
Electrostatics II (15 Lessons)
Heating Effect of Electric Current (10 Lessons)
Quantity of Heat (20 Lessons)
Gas Laws (15 Lessons)

FORM IV - PHYSICS SYLLABUS

Thin Lenses (20 Lessons)
Uniform Circular Motion (10 Lessons)
Floating and Sinking (15 Lessons)
Electromagnetic Spectrum (15 Lessons)
Electromagnetic Induction (20 Lessons)
Mains Electricity (10 Lessons)
Cathode Rays and Cathode Ray Tube (10 Lessons)
X-rays (8 Lessons)
Photoelectric Effect (15 Lessons)
Radioactivity (15 Lessons)
Electronics (10 Lessons)

K.C.S.E Physics Q & A - MODEL 2019PP2QN19

K.C.S.E Physics Q & A - MODEL 2019PP2QN19

K.C.S.E Physics Q & A - MODEL 2019PP1QN18

K.C.S.E Physics Q & A - MODEL 2019PP1QN18

K.C.S.E Physics Q & A - MODEL 2019PP1QN17

K.C.S.E Physics Q & A - MODEL 2019PP1QN17

K.C.S.E Physics Q & A - MODEL 2019PP1QN16

K.C.S.E Physics Q & A - MODEL 2019PP1QN16

K.C.S.E Physics Q & A - MODEL 2019PP1QN15

K.C.S.E Physics Q & A - MODEL 2019PP1QN15

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FORM I - PHYSICS SYLLABUS

FORM II - PHYSICS SYLLABUS

FORM III - PHYSICS SYLLABUS

FORM IV - PHYSICS SYLLABUS

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