Question Library

Sound waves are longitudinal waves which cannot be plane polarized as polarization is a characteristic of transverse waves only.

(a) Surface tension is the force per unit length acting in the surface at right angles to one side of a line drawn in the surface of a liquid. It can be defined as the property of a liquid that makes it behave as if its surface is an elastic skin. (b) Methods of reducing surface tension are by adding: - Soap - alcohol - oil - detergent - increasing the temperature.

Air molecules near the ceiling get cooled, become denser and sink while warmer air moleculus below being lighter rise to the top, get cooled, become denser and sink once more, thereby sets up conventional current.

(a) Fluorescent tube operate on the principle of electrical discharge through a gas at very low pressure and very high voltage. (b) Factors which determine the colour of light in a fluorescent tube are: -voltage across the tube -nature of gas in the tube -nature of powder coating inside the tube.

The ray will bend upward. The direction of motion of the charge is due to the force acting on it which is mutually perpendicular to the direction of the magnetic field and the moving charge.

(a) Wave - particle duality of light means that light exists in two forms - wave and particle. (b)(i) Wave nature - it has properties such as reflection, refraction, diffraction, polarization and interference. (ii) Particle nature such as - Photo-electricity, momentum, radiation of energy from hot bodies and emission and absorption of light.

(a) Principle of conservation of linear momentum states that if two or more bodies collide in a closed system, the total momentum after the collision is equal to the total momentum before the collision. (b) The principle of action of a propelled rocket is that gas burnt within the combustion chamber of the rocket engine is expelled downwards through the exhaust (tail nozzle) at very high speed, hence an equal and opposite momentum is given to the rocket which moves the rocket upward. (c) The motion is not simple harmonic because: -there is no equilibrium position -acceleration of the ball is not directly proportional to displacement -acceleration of the ball is not directed towards a fixed point. (d)(i) Both balls will hit the ground at the same time. (ii) All free falling objects fall at the same rate because they are pulled towards the earth by gravity and accelerate at a constant rate. (e)(i) Charge in momentum = m(v-u) = 0.10(13 - 17) = 3 kgms\(^{-1}\) (ii) Average force F = \(\frac{\text{change in momentum}}{\text{time}}\) = \(\frac{3}{0.15} = 20N\)

(a)(i) A machine is a device in which an effort applied at one end is used to overcome a load at another point. Machine makes work easier. (ii) Uses of gears are: - to change speed to change direction of motion - to magnify force. (iii) Velocity ratio of a gear wheel is the ratio of number of teeth on driven wheel to number of teeth on driving wheel OR Velocity ratio = \(\frac{\text{Time rate of revolution/speed/radius of driven wheel}}{\text{Time rate of revolution/speed/radius of driving wheel}}\) (iv) To increase the mechanical advantage, the driving gear is made smaller with fewer teeth than the driven gear. (b) Number of teeth on driven gear = 12. Number of teeth on driving gear = 18. (i) V.R. = \(\frac{\text{no. of teeth on driven gear}}{\text{no. of teeth on driving gear}}\) = \(\frac{12}{8} = \frac{2}{3}\) (ii) Efficiency - \(\frac{M.A}{V.R}\) x 100% = x 100% = \(\frac{L/E}{V.R}\) x 100% 90 = \(\frac{70/E}{2/3}\) x 100% (iii) This is due to: - Friction between the tyres and load. - Friction between chain and gear.

Critical angle is the angle of incidence in the denser medium when the angle of refraction in the less dense medium is 90^\circ. (b) Deviation of a ray in a triangular prism is determined by the factors: - Angle of incidence - Refracting angle of the prism, and - Refractive index of the prism material. (c) A = 2r = 2 x 29 = 58\(^o\) But n = \(\frac{sin \frac{1}{2} (A + Dm)}{sin \frac{1}{2}A} \) sin \(\frac{1}{2}\)(A + Dm) = n sin A \(\frac{1}{2}\)A 58 + Dm = 93.32 - 58 = 35.32\(^o\) (d) Angle P = 45^\circ - 20^\circ = 25^\circ But Angle Q = 180^\circ- 60^\circ = 120^\circ P +Q + R = 180^\circ Hence R = 180 - (P + Q) =180 - (25 + 120) = 35^\circ (ii) n = \(\frac{Sini}{sinP} = \frac{sin45^o}{sin45^o} = 1.673\) (iii) n = \(\frac{sini}{sine} = \frac{sine}{sinR} = \frac{sinee^o}{sin35^o}\) = 1.673 = \(\frac{sine}{sin35^o}\) e = sin\(^{-1}\) (1.673 x sin 35\(^o\)) = 73.7\(^o\) (iv) D = (i + e) - A = (45 + 73.3) - 60\(^o\) = 58.3\(^o\)

(a) Magnetic line of force is defined as an imaginary line in a mangetic field along which a free or isolated north pole would move. OR, it is an imaginary line in a magnetic field such that the targent to it at any point gives the direction of the field at that point. (b) F = 1BL Sin\(\theta\) (i) When wire is parallel to the field F = IBL = 4x 2 x 0.1 =0N (ii) When force is maximum F = IBL Sin90^\circ = 4 x 2 x 0.1 x Sin90^\circ= 0.8N (iii) When the wire is at 60^\circ to the field F = IBL Sin\(\theta\) = 4 x 2 x 0.1 x Sin60^\circ = 0.693N (c) Magnets are stored in pairs with their poles adjacent, placing soft iron pieces called keepers across their ends. The keepers become magnets by induction decreasing the reluctance of the air gap; hence both magnets and keepers form closed loops with no free poles preventing demagnetization . (d) True bearing = 15 + 10 = N25^\circW.

(a)(i) X-rays can produce photographs of fractures in bones; it can pass through fractures but cannot penetrate bones. (ii) Uses of x-ray other than in medicine: —detection of cracks in metallic products —detection of alternations in art works —detection of fake gems —examination of bags and luggage —identification of chemical elements and their isotopes. (b) The energy transformations: Electrical energy —> Heat energy —> Kinetic energy —> Electromagnetic energy —> X-rays and Heat energy. (c)(i) Dangers of over exposure to x-rays are: — Cell mutation, i.e. change in cell genetic codes. — Leukaemia: the destruction of living cells, tissues and organs. — Skins harm, causes skin burn and tanning. (ii) A person working on x-rays should take the following precautions: — wear lead protective coats — wear dosimeter — wear protective goggles — go for routine regular medical check-up. (d)(i) K.E. = eV = 1.6x10\(^{-19}\) x 33 x 10\(^3\) = 5.28 x 10\(^{-15}\)J V = \(\sqrt{\frac{2K.E}{m}} = \sqrt{\frac{2 \times 5.28 \times 10^{-15}}{9.1 \times 10^{-31}}}\)

R.d = \(\frac{\text{weight of object in air}}{\text{upthrust in water}}\) = \(\frac{10.5}{10.5 - 6.8} = \frac{10.5}{3.7} = 2.84\)

M\(_{(g)}\) \(W_1\) \(W_2\) \(W_3\) U=(\(W_1\)-\(W_2\)) V=(\(W_1\)-\(W_3\)) 50 0.50 0.43 0.45 0.07 0.05 100 1.00 0.90 0.88 0.10 0.17 150 1.50 1.30 1.33 0.20 0.17 200 2.00 1.73 1.75 0.27 0.25 250 2.50 2.15 2.20 0.35 0.30 SEE THE GRAPH ABOVE Slope, s = \(\frac{y_{2}-y_{1}}{x_{2}-x_{1}} = \frac{0.275-0.10}{0.32-0.125}\) s = \(\frac{0.175}{0.195}\) = 0.9 Precautions: i - ensured that I avoided errors due to parallax while taking the readings on the spring balance. - made sure the mass is totally immersed in water and liquid - ensured the retort stand and clamp are well tightened. (b)i. Archimedes' principle states that when a body is totally immersed in a fluid (liquid or gas), it experiences an upthrust that is equal to the weight of the fluid displaced. Mass of brass = 20g = 2 x 10\(^{-2}\)kg Density of kerosine 8.0 x 10\(^{2}\)kgm\(^{-3}\) g = 10ms\(^{-2}\)kg Density of brass = 8.0 x 10\(^{3}\)kgm\(^{-3}\)kg Volume of brass = \(\frac{m}{D} = \frac{2 \times 10}{8 \times 10^{3}}\) = \(\frac{2}{8}\) x 10\(^{-2-3}\) = 0.25 x 10\(^{-5}\)m\(^{3}\) Volume of brass = 2.5 x 10\(^{-6}\)m\(^{3}\) Therefore, the mass of brass in kerosene m = Density x volume of brass = 8.0 x 10\(^{2}\) x 2.5 x 10\(^{-6}\)m\(^{3}\) = 20 x 10\(^{-4}\) Reading on the spring balance 20 x 10\(^{-4}\) = 20 x 10\(^{-3}\) N

S/N M\(_{(g)}\) V(cm\(^{3}\)) V\(^{-1}\)(cm\(^{-3}\)) 1 500 9.30 0.11 2 1000 7.40 0.14 3 1500 6.40 0.16 4 2000 5.40 0.19 5 2500 4.60 0.22 Slope, s = \(\frac{y_{2} - y_{1}}{x_{2} - x_{1}} = \frac{2425 - 725}{0.12 - 0.125}\) \(\frac{1700}{0.086}\) = 20,000 Evaluation S = 20,000 K = s\(^{-1}\) = \(\frac{1}{20,000}\) = 5 x 10\(^{-5}\) Precautions; i - ensured that the retort stand and clamp are well tightened. - avoided error due to parallel when taking my readings. - made sure that the syringe is not on zero error. (b)i. The quantities of the gas above the plunger increase ii. While the quantities of the gas below the plunger decrease. iii. Weight

S/N OP(\(_{cm}\)) I(\(_{A}\)) V(\(_{v}\)) 1 20.0 0.13 1.08 2 30.0 0.14 0.97 3 40.0 0.15 0.85 4 50.0 0.16 0.74 5 60.0 0.17 0.60 Slope, s = \(\frac{y_{2} - y_{1}}{x_{2} - x _{1}} = \frac{0.85 - 0.30}{0.20 - 0.5}\) \(\frac{0.55}{0.05}\) = 11 When I = o V = 3.15v Precautions; i - ensured that the key was open whenever the circuit was not in use so as to avoid the cells being run down. - ensured there was no zero error in the ammeter and the voltmeter by making necessary adjustments before taking my readings. - ensured that the jockey did not scrap the potentiometer wire. - ensured that the electrical wires were tightly connected to the terminals in order to avoid current fluctuations. (b)i. Lead-acid accumulator Leclanche cell (i). It has the capacity to supply large current for a long time (ii). It can be charged It has no such capacity It cannot be recharged ii. e.m.f = 2V r = 1\(\Omega\) (internal resistance) R = 9\(\Omega\) (external resistance) Calculate the potential drop across the cell. By formula; E = I(R +r) 2 = I(9 + 1) 2 = 101 I = \(\frac{2}{10}\) = 0.2A Therefore, the p.d drop across the cell is Ir. = 0.2 x 1 = 0.2V