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PHYSICS SCIENCE PAPER - 1 (Two hours) Answers to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 15 minutes. This time is to be spent in reading the question paper. The time given at the head of this Paper is the time allowed for writing the answers. Attempt all questions from Section I and any four questions from Section II. The intended marks for questions or parts of questions are given in brackets [ ]. SECTION I (40 Marks) (Attempt all questions from this Section.) Question 1. (a) Which physical quantity does the electron volt measure? How is it related to the SI unit of this quantity? [2] (b) What should the angle between force and displacement be to get the (i) Minimum work; (ii) Maximum work? [2] (c) By drawing diagram, given an example of a body where CG lies outside the body. [2] (d) The work done by the heart is 1 joule per beat. Calculate the power of the heart if it beats 72 times in one minute. [2] (e) Mention two properties of a wave: one property which varies and the other which remains constant when the wave passes from one medium to another. [2] Question 2. (a) Two waves of the same pitch have their amplitudes in the ratio 4: 3. i) What will be the ratio of their loudness? ii) What will be the ratio of their frequencies? [2] (b) State the energy changes which take place when a bulb glows, when a torch light is switched on. (c) A moving body weighing 400 N possesses 500 J of kinetic energy. Calculate the velocity with which the body is moving, (g = 10 m s 2) [2] [2] 1 Physics Pre - Board Exam 2020 - 21 Class 10 Strawberry Fields High School (d) (i) What is meant by the statement, the critical angle for diamond is 24 ? (ii) How is the critical angle of a material related to its refractive index? [2] (e) Why is the mechanical advantage of movable pulley 2? [2] Question 3. (a) Name any two electromagnetic waves which have a frequency higher than that of violet light. State one use of each. [2] (b) How does a trawler man catch fish in deep water? [2] (c) Why does the temperature of the surroundings start falling when the ice of a frozen lake starts melting? [2] (d) Four resistances 2.0 ohm each are joined end to end to form a square ABCD. Calculate the equivalent resistance of the combination between any two adjacent comers. [2] (e) In a three-pin plug, why is the earth pin made longer and thicker than the other two pins? [2] Question 4. (a) State the conditions required for total internal reflection of light to take place. (b) A ray of monochromatic light enters a liquid from air as shown in the given diagram: i) [2] Copy the diagram and show in the diagram the path of the ray of light after it strikes the mirror and reenters the medium of air. ii) Mark in your diagram the two angles on the surface of separation when the ray of light moves out from the liquid to air. [2] (c) The speed of light in glass is 2 x 105 km s 1. What is the refractive index of glass? (d) How many alpha and beta particles are emitted when Uranium nucleus (e) Which of the radioactive radiations (i) can cause severe genetical disorders (ii) are deflected by an electric field? 238 92 U decays to Lead [2] 206 82 Pb ? [2] [2] 2 Physics Pre-Board Exam 2020 - 21 Class 10 Strawberry Fields High School SECTION II (40 Marks) (Attempt any four questions from this Section.) Question 5. (a) (i) State the law of conservation of energy. (ii) Name the chief energy transformation that occurs (A) in a loudspeaker; (B) in an electric cell (Primary). [3] (b) Define 'joule', the SI unit of work and establish a relationship between the SI and CGS unit of work. [3] (c) The above figure shows the combination of a movable pulley P1 with a fixed pulley P2 used for lifting up a load W. (i) State the function of the fixed pulley P2 (ii) If the free end of the string moves through a distance x, find the distance by which the load W is raised. (iii) Calculate the force to be applied at C to just raise the load W = 20 kgf, neglecting the weight of the pulley P1 and friction. [4] Question 6. (a) Water falls from a height of 50 m. Calculate the rise in the temperature of water when it strikes the bottom. (g = 10 ms 2; Specific heat capacity of water = 4200 J/kg C) 3 [3] Physics Pre-Board Exam 2020 - 21 Class 10 Strawberry Fields High School (b) (i) Under what condition resonance occur? (ii) Why is loud sound heard during acoustic (sound resonance) [3] (c) i) A person is tuning his radio set to a particular station. What is the person trying to do to tune it? ii) Name the phenomenon involved in tuning the radio set. iii) Define the phenomenon named by you in part (ii). [4] Question 7. (a) A lens forms an upright and diminished image of an object when the object is placed at the focal point of the given lens. i) Name the lens. ii) Draw a ray diagram to show the image formation. [3] (b) A glass slab is placed over a page on which the word VIBGYOR is printed with each letter in its corresponding colour. A. Will the image of all the letters be in the same place? B. If not, state which letter will be raised to the (i) maximum and (ii) minimum. Give a reason for your answer. [3] (c) (i) What is meant by refraction? (ii) Express the refractive index n of a medium: A. in terms of the velocity of light; B. in terms of the angle of incidence I in air and the angle of refraction r in a denser medium. (iii) If a ray of light passes from medium I to medium II without any change of direction, what can be said about the refractive indices of these media (angle I is not 00)? 4 [4] Physics Pre-Board Exam 2020 - 21 Class 10 Strawberry Fields High School Question 8. (a) A radar is able to detect the reflected waves from an enemy aeroplane, after a time interval of 0.02 milliseconds. If the velocity of the waves is 3 x 108 ms-1, calculate the distance of the plane from the radar. [3] (b) A piece of ice is heated at a constant rate. The variation of temperature with heat input is shown in the graph below: (i) What are represented by AB and BC? (ii) What conclusion can you draw regarding the nature of ice from the above graph? [3] (c) A cell of emf 2 V and internal resistance 1.2 is connected with an ammeter of resistance 0.8 and two resistors of 4.5 and 9 as shown in the diagram below: i) What would be the reading on the ammeter? ii) What is the potential difference across the terminals of the cell? [4] Question 9. (a) An electrical appliance is rated 1500 W, 250 V. This appliance is connected to 250 V mains. Calculate: (i) the current drawn, (ii) the electrical energy consumed in 60 hours, 5 Physics Pre-Board Exam 2020 - 21 Class 10 Strawberry Fields High School (iii) the cost of electrical energy consumed at Rs. 2.50 per kWh. [3] (b) The relationship between the potential difference and the current in a conductor is stated in the form of a law. i) Name the law. ii) What does the slope of V-I graph for a conductor represent? iii) Name the material used for making the connecting wire. [3] (c) In the figure given below. A, B and C are three ammeters. The ammeter B reads 0.5 A (All the ammeters have negligible resistance.) Calculate: (i) the readings in the ammeters A and C. (ii) the total resistance of the circuit. [4] Question 10. (a) (i) What are isobars. (ii) Give two examples of isobars. (i) Mention two important precautions that should be taken while handling radioactive materials. (ii) State one use of radioisotopes. (i) Show by equations, the effect on the proton number Z and mass number A of the parent [3] (b) [3] (c) nucleus brought about by the two types of radioactive decay. (ii) Out of alpha, beta and gamma radiations A. Which radiation is the most penetrating? B. Which radiations are negatively charged? [4] 6 Physics Pre-Board Exam 2020 - 21 Class 10 Strawberry Fields High School
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