enwaecphysics2012

more

1. The derived unit of pressure can be expressed as Kg ms-2 Kg m-1 s-2 Kg m-2 s-2 Kg m-1s2 The diagram above illustrates trapped air in a syringe placed in water that is gradually heated. It is observed that the piston rises as the temperature of the water rises. Which of the following statements explains this observation? Frequency of collision of trapped air molecules with walls of the syringe is more. Molecules of trapped air expand more. Number of molecules of trapped air increases. Speed of the trapped air molecules decreases. 3. Which of the following devices is used to determine the relative density of an acid? Manometer Hydrometer Hypsometer Hygrometer 4. A block of wood density 0.6gcm-3, weighing 3.06N in air, floats freely in a liquid of density 0.9gcm-3. Calculate the volume of the portion immersed. (g=10ms-2). 510 cm3 340 cm3 254 cm3 170 cm3 5. A metal ball of weight W falls through a column of glycerine of viscosity V. If the ball experiences an upthrust U and terminal velocity is attained, then W>U+V W=U+V W=U-V W < U+V 6. Which of the following substances is the most volatile at room temperature? Water Diesel Petrol Kerosene 7. The movement of fluid up or down a narrow tube is Osmosis Brownian motion Capillarity Diffusion 8. A bird flies at 10ms-1 for 3s, 15ms-1 for 3s and 20ms-1 for 4s. Calculate the bird’s average speed. 4.5 ms-1 15.0 ms-1 15.5 ms-1 51.7 ms-1 9. Which of the following velocity-time graphs does not represent an accelerated motion? 10. The time of flight of a projectile motion is given by the expression (Usin θ)/g (U sinθ)/2g (2U sinθ)/g (U sin⁡2θ)/g

ANSWERS

11. An object is dropped from the top of a tower. If it takes 4s for it to reach the ground, calculate the height of the tower. (g=10ms-2, ignore air resistance). 20m 40m 80m 160m 12. When a body is slightly tilted, it is found that its centre of gravity is slightly raised. What is the state of equilibrium of the body? Unstable Stable Neutral Cannot be determined 13. A simple pendulum makes 50oscillaitons in one minute. Determine its period of oscillation. 0.04s 0.83s 1.20s 50.00s 14. The tendency for a stationary body to continue to remain at rest when a force is applied to it is known as Friction Impulse Inertia Momentum 15. A resultant force of magnitude 15N acts on a body of mass 250g. Calculate the magnitude of the acceleration. 0.06ms-2 3.75ms-2 16.67ms-2 60.00ms-2 16. A girl stands on a scale in a lift. If the reading on the scale is less than her weight, then the lift is moving Upward at uniform speed Upward with uniform acceleration Downward with uniform speed Downward with uniform acceleration 17. The S.I. unit of heat is Joule Kelvin Watt Ampere 18. A body is pulled through a distance of 500m by a force of 20N. If the power developed is 0.4kW, calculate the time for which the force acts. 250.0 s 25.0 s 2.5 s 0.5 s 19. A metal sheet of area 100 cm3was heated through 70℃. Calculate its new area if the linear expansivity of the metal is 0.000017K-1. 100.06 cm3 100.12cm3 100.24cm3 100.36cm3 20. The thermopile is a device for detecting Radioactive radiations Radiant energy X-rays The presence of electrons

ANSWERS

21. In the formation of sea breeze, wind blows from Sky to land Sea to sky Land to sea Sea to land 22. A piece of copper of mass 20g at a temperature of 110℃ was dropped into a mixture of ice water at 0℃. If the final steady temperature of the mixture is 0℃, calculate the amount of ice that melted. [Specific heat capacity of copper=0.4 Jg-1K-1 Specific latent heat of fusion of ice =330 Jg-1] 0.37 g 0.60 g 2.40 g 2.70 g 23. Which of the following factors decreases the rate of evaporation of a liquid? Increase in pressure over a liquid Lowering the boiling point Decrease in humidity Wind 24. When two waves are superimposed on each other, the following occurrences are possible, except Nodal lines Anti-nodal lines Stationary waves Dispersion 25. Which of the following properties of waves is exclusive to transverse waves? Reflection Interference Diffraction Polarization 26. An object of height 2.5cm is placed 20cm from a convex mirror of focal length 10 cm. Calculate the height of its image. 2.5 cm 3.0 cm 5.0 cm 25.0 cm 27. A ray of light passes from air to water to glass to air. Given that the refractive index for light for passing from air to water is 4/3 and air to glass is3/2, calculate the refractive index of glass relative to water. 0.50 0.67 0.75 1.13 28. An object is placed at a point X between the focal point F and the optical centre C of a diverging lens. If F’ is the focal point on the other side of the lens, the image of the object is formed between F and X X and C C and F’ F’ and 2F’ 29. An object is placed 10 cm from a converging lens of focal length 15 cm. Calculate the magnification of the image formed. 3.0 1.5 0.6 0.3 30. A telescope is said to be in normal adjustment when the Focal length of objective is greater than that of the eyepiece Focal length of the eyepiece is greater than that of the objective Focal length of the eyepiece is equal to that of the objective Objective focal point coincides with that of the eye piece

ANSWERS

31. The sound heard by a person after the reflection of the sound generated by him is called Reverberation Resonance Echo Audibility 32. Which of the following sets of coloured light is/are secondary colours? Red, Blue and Green Blue, Cyan and Magenta Green, Magenta and Yellow Yellow, Cyan and Magenta I and II only II and III only IV only I, II and IV only 33. Which of the following diagrams correctly illustrates the vibration of air column for second harmonics in an open pipe? 34. When two like charges are brought together, the potential energy of the system formed will Increase because work is done against the field Increase because work is done by the field Decrease because work is done by the field Decrease because work is done against the field 35. Two capacitors, each of capacitance 2μF are connected in parallel. If the p.d. across them is 120V, calculate the charge on each capacitor. 6.0 × 10-5C 1.2 × 10-4C 2.4× 10-4C 4.8× 10-4C 36. Which of the following properties is an advantage of a lead-acid accumulator over an alkaline accumulator? Possesses low internal resistance Can be recharged Has shorter life span Possesses higher emf 37. Six dry cells each of emf 2.0 and internal resistance of 1.0Ω are connected in parallel across a load of 3.0Ω. Calculate the effective current in the circuit. 0.63 A 0.50 A 0.31 A 0.22 A 38. Two similar cells are used to light two similar lamps as illustrated in the diagrams above. In which of the circuit diagrams are the lamps brightest? P Q R S 39. A 12Ω resistor dissipates a 8kJ of heat in 20s. Calculate the current through the resistor. 5.8 A 6.9 A 30.0 A 33.3 A 40. A bar magnet is broken into two pieces. Which of the following diagrams correctly illustrates the polarities of the pieces?

ANSWERS

41. The magnetic relay is a device used for Timing in sports Storing in magnetic field Reading the magnitude of magnetic flux Controlling another circuit carrying larger current 42. The core of a transformer is usually laminated in order to Reduce magnetic flux leakage Reduce eddy current Prevent vibration of the transformer Make magnetic reversal in the core much easier 43. Which of the following modes is the most economical method of transmitting electrical power over long distances? Alternating current at low voltage and high current Alternating current at high voltage and high current Alternating current high voltage and low current Direct current at low voltage and high current 44. An inductor is connected to a 24V, 50Hz mains supply. If the current through the inductor is 1.5 A, calculate the inductance of the inductor. (π=22/7) 8.0 × 102H 7.5× 100H 1.6× 100H 5.1× 10-2H 45. In a R-C circuit Irms leads Vrms by 60° Irms lags Vrms by 60° Vrms lags Irms by 90° Vrms leads Irms by 90° 46. An atom in an excited state is one whose Potential energy is minimum Potential energy is maximum Electrons are in the conduction band Electrons have moved to higher energy level 47. A metal with a work function of 3.0eV is irradiated with ultraviolet light of energy 4.0eV. The kinetic energy of the ejected electron is 1.0 eV 3.0 eV 4.0 eV 7.0 eV 48. Which of the following statements about x-rays is correct? X-rays Are produced when a metal surface is irradiated with ultraviolet light Are produced when a metal target is used to block fast moving electrons Have long wavelengths and are therefore very penetrating Are not part of the electromagnetic spectrum 49. Which of the following arrangements of radiations is in order of decreasing penetrating power? α, β,  α, , β β, , α , β, α 50. Which of the following radiations emitted in radioactive decay has momentum a fairly high penetrating power is deflected by a magnet? Alpha particle Beta particle Gamma radiation X-radiation

ANSWERS