Correct shape in relation to h and t correct shape in relation to h and t2
h varies parabolically with t h varies linearly with t2
A particle is projected horizontally at 15ms-1 from a height of 20m.
[g = 10 ms-2]
Let R represent the horizontal distance covered at time, t.
h = ½ gt2
20 = ½ x 10 x t2
t = 2 s
R = ut
= 15 x 2
Mercury does not wet glass because (force of) cohesion/attraction of mercury molecules is greater than (force of) adhesion/attraction between glass and mercury molecules.
Water wets glass because (force of) adhesion/attraction between glass and water molecules is greater than (force of) cohesion/attraction of water molecules.
(a) Cations – are positive ions that are attracted to the cathode (during electrolysis)
Correct diagram/sketch: labeling cathode, anode and electrolyte.
This question on polarization was very popular among the candidates and their responses were quite commendable.
a) If the same quantity of electricity is passed through different voltameters/electrolytes connected in series the masses of the substances liberated/deposited during electrolysis is (directly) proportional to their chemical equivalents.
OR The mass of an element deposited/liberated during electrolysis is (directly) proportional to the chemical equivalent of the element.
(b) Let e represent the electronic charge.
e = Faraday’s constant
= 9.6 x 104
6. 0. x 1023
= 1.60 x 10-19C
Explain the following terms:
- tensile stress;
- Young’s modulus
(a) Tensile stress is the ratio of force to cross-sectional area of a wire/rod
It is expressed in Newton per metre squared (Nm-2)
(b) Young’s modulus is the ratio of tensile stress to tensile strain. It is expressed in Newton per metre squared. (Nm-2)
|a) Define diffusion.|
(b) State two applications of electrical conduction through gases.
(a) Diffusion is the process by which substances mix (intimately) with one another due to the random motion of their molecules.
(b) Applications of electrical conduction through gases include:.
– In advertising industry/Neon signs
– In lighting/fluorescent tubes
– Identification of gases
– Cathode ray oscilloscope/T.V. tubes
(a) Properties of cathode rays:
- are negatively charged.
- travel in straight line in field free space.
- are deflected by electric/magnetic field.
- possess(kinetic) energy.
- possess momentum.
(b)(i) The intensity of cathode rays may be increased by raising the temperature of the cathode/increasing the current through the heater.
(ii) The energy of cathode rays may be increased by raising the potential difference between
the anode and the cathode/the anode potential.
Make at least 3 well-spaced pin holes round the edge of the cardboard. Clamp the pin horizontally and suspend the cardboard on it through one of the pin-holes such that the cardboard can swing freely
Hang the simple pendulum on the same pin and let its string be very close to the cardboard.
When the whole system is at rest (or in equilibrium) trace the plumbline on the cardboard. Repeat the procedure for each of the two other pin holes.
The point at which the (three) traced lines intersect is the centre of gravity of the cardboard.
– Repeat procedure
– Pin rigidly and firmly held by retort stand and clamp
– Allow the simple pendulum to rest before tracing the shadow of
the plumbline on the cardboard.
– The string to be close to the cardboard
Both axes correctly labelled
Any correct shape of graph showing acceleration segment
- Acceleration = gradient of AB
- Total distance covered = area under the graph
– At least one axis labelled
– correct shape of graph
Let V1 = maximum velocity after 20 sec.
V2 = maximum velocity after 30 sec.
(i) Then V1 = 6
∴ V1 = 120 ms-1
Also V2 – V1 = 4
V2 – V1 = 40
V2 = 120 + 40
V2 = 160 ms-1
Maximum speed = V2 = 160ms-1
(ii) Total distance covered = Area of Δ + Area of trapezium after 1st 30 seconds
= ( ½ x 20 x 120) + ½ (120 + 160) x 10
= 1200 + 1400
(iii) Average speed = Total distance
= 2600 30
= 86.67 ms-1
|(a) Explain why it is not advisable to sterilize a clinical thermometer in boiling water at normal atmospheric pressure.|
(b) State the effect of an increase in pressure on the
The graph shown above is that of the saturated vapour pressure (s.v.p.) of water against temperature.
d) A thread of mercury of length 20 cm is used to trap some air in a capillary tube with uniform cross-sectional area and closed at one end. With the tube vertical and the open end uppermost, the length of the trapped air column is 15cm. Calculate the length of the air column when the tube is held:
ii) vertically with the open end underneath. [Atmospheric pressure = 76 cmHg ]
a) A clinical thermometer has small temperature range. The glass will crack/burst due to excessive pressure created by expansion of mercury.
(b) Increase in pressure
(i) increases the boiling point;
(ii) decreases the melting point.
- At the boiling point of pure water, the saturated vapour pressure (s.v.p)
of the water is equal to the external atmospheric pressure.
Volume V is proportional to length Ɩ stated or implied
(i) P1V1 = P2 V2 implies P1 Ɩ1 = P2Ɩ2
(76 + 20) 15 = 76 x Ɩ2
Ɩ2 = 96 x 15
Ɩ2 = 18.95 cm
(ii) P1 Ɩ1 = P3 Ɩ3
(76 + 20) 15 = (76 – 20) x Ɩ3
Ɩ3 = 96 x 15
Ɩ3 = 25.7l cm
(a) State two differences between a sound wave and a radio wave.
(b) Explain why a vibrating tuning fork sounds louder when its stem is pressed against a table top than when held in air.
(c)State two conditions necessary for the:
(a) Differences between a sound wave and a radiowave
|Sound wave||Radio wave|
|is a mechanical wave||is an electromagnetic wave|
|is longitudinal||is transverse|
|has speed less than speed of light.||has speed equal to that of light|
|requires a material medium for propagation/cannot travel through vacuum.||does not require a material medium for propagation/can travel through vacuum.|
(b) The vibrating tuning fork forces the table top to vibrate. The table top has a much larger area and is therefore in contact with a larger volume of air undergoing vibration. Hence, sound heard is amplified.
(c) Conditions necessary for:
(i) production of stationary wave
– Two waves must be traveling in opposite directions.
– Incident and reflected waves must have the same frequency/wavelength.
– Incident and reflected waves must have equal amplitude.
– There must be superimposition.
– There must be a barrier
(ii) formation of interference wave pattern
– Two sources must be involved.
– The two sources must be coherent/have a constant phase difference as well as the same frequency and amplitude.
– The waves that are interfering must have the same amplitude
– The distance between the sources must be of the order of the wavelengths of the waves.
(iii) total internal reflection
– The wave must be traveling from a denser medium to a less dense medium
– The angle of incidence of the wave in the denser medium must be greater than the critical angle for the medium.
(ii) Sin (A + dm)
n = 2
Sin (60 + 41)
(a) State two essential differences between a moving coil galvanometer and a d.c. generator.
(a) Differences between a d. c. generator and a moving coil galvanometer.
|D. C. generator||moving coil galvanometer|
|converts mechanical energy to electrical energy||converts electrical energy to mechanical energy.|
|uses split rings or commutator||uses hair springs.|
|rotation of coil is continuous||rotation of coil is incomplete|
|uses carbon brushes (as terminals)||uses jeweled bearings (as terminals)|
(b) Eddy currents are currents induced in a conductor when subjected to varying magnetic field.
Any valid additional information e.g.
- eddy current flows in a circular path or closed loops;
- eddy current generates heat;
- eddy current cannot flow through gaps or slots;
- The currents move in such a direction as to oppose the change producing them.
Devices in which eddy currents are applied
- pointers of sensitive electric meters
- sensitive mass balances
- brakes in large electric motors
- speedometers in automobiles
- detection of cracks in railway tracks
- detection of metals
(c) Principle on which a potentiometer is based
When a steady current is allowed to pass through a uniform wire, equal lengths of the wire will have equal potential differences.
The p.d across a length of a wire is (directly) proportional to the length provided the wire has a uniform cross section.
Vector diagram showing
VL with arrow
VC with arrow
VR with arrow
V2 = VR2 + (VL – VC)2
1102 = 802 + (40 – Vc)2
1102 -802 = (40 – Vc)2
(40 – Vc ) = (110 + 80) (110 – 80)
40 – VC = + 75.5
VC = 40 + 75.5
VC = 115.5V
(ii) VC = I X c
Xc = Vc / = 1 /
I 2π¦C 2
∴ C = I/2π¦VC = 2 x 3.14 x 60 x 115.5
C = 0.0000459 C = 45.9 x 10-6 F or 46mF
(a)(i) Emission line spectra consist of distinct and separate bright lines of definite wavelengths on a dark background.
Any valid additional information e.g
– They are obtained when light from a luminous source undergoes dispersion and is observed directly.
– When an electron moves from one energy level to another energy level, line spectra are observed
– The colour of the spectra is a characteristic of the source.
(ii) Line absorption spectra are obtained when light passes through a cool gas and certain wavelengths of the light are absorbed. This gives series of dark lines, each corresponding to one of the wavelengths absorbed.
When radiation of appropriate frequency falls on the cathode (with photosensitive surface) electrons are emitted. Because the anode is positive with respect to the cathode, the electrons are attracted to the anode. The electrons flow completes the circuit and current flows.
(c)(i) Wave properties of X-rays
(ii) Uses of X-rays other than in medicine
- to study crystal structures
- to detect presence of cracks in welded parts
- in artistic works for determining the authenticity of such works
- at security check points to scan
- X-ray spectroscopy for identifying isotopes of elements.
ΔE = Ei – Ef
= – 1.6 – (- 10.4)
= 8.8 e V or 1.41 x 10-18 J
E = hf = hc/λ
λ = hc/E
= 6. 6 x 10-34 x 3 x108
8.8 x 1.6 x 10-19
λ = 1.4 x 10-7 m