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A.G.C. School, Rupaidiha Preliminary Examination 2020-2021 SCIENCE Paper (PHYSICS) 1 (Two Hours) Maximum Marks: 80 Class - X _____________________________________________________________ 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 the 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) Study the diagram alongside carefully and calculate the resultant moment of force about (a) point P and (b) point R which is exactly in the middle of the two processes. [2] (b) State the energy changes in the following cases while in use: (i) A piece of magnesium burns in air, (ii) Food eaten by human. (c) (i)What is normal reaction force? (ii) How are gravitational units of force related with the absolute units of force (d) State two factors affecting the turning effect of force. (e) State work energy theorem. Write a mathematical relation expressing it. Question 2 (a) Draw a diagram to show how a single pulley can be used so as to have its ideal Mechanical advantage is equal to 2 (b) Establish the relation MA = VR x . (c) Define specific heat capacity and state its SI unit. [2] [1] [1] [2] [2] [1] [1] [2] (d) The melting point of naphthalene is 80 C and the room temperature is 30 C. A sample of liquid naphthalene at 100 C is cooled down to the room temperature. Draw a temperature time graph to represent this cooling. In the graph, mark the region which corresponds to the freezing process. [2] (e) Define fuse and write its characteristics. [2] (f) How does the resistance of a metallic wire depends on the following: (i) The length of the wire (ii) the temperature of the wire? [2] Question 3 (a) (i) What is the ratio of velocities of light of wavelength 4000 A and 8000 A in vacuum. [1] (ii) What is the wavelength range of ultra-violet radiations in nm? [1] (b) The power of lens is 2.5 D. [2] (i) Find its focal length. (ii) Name the type of lens. (c) What is dispersion of light? What is its cause? [2] 12 (d) What is the wavelength of the wave whose frequency is 10 Hz? Name the electromagnetic wave. [2] (e) Displacement distance graph of two sound waves A and B , travelling in a medium, are as shown in the diagram below Study the two sound waves and compare their: (i) Amplitudes (ii) Wavelengths Question 4 (a) Calculate the effective resistance of the circuit. [2] (b) State two ways by which the frequency of transverse vibration of a stretched string can be increased. [2] (c) Identify the following wires used in a household circuit for which purpose: [2] (i) Nichrome wire. (ii) Copper wire. (d) (i) Define Isotopes. [1] (ii) How does the position of an element change in the periodic table when it emits out an alpha particle? [1] (e) (i) What will an alpha particle change into when it absorbs one electron? [1] (ii) Rewrite and complete the following nuclear reaction by filling in the blanks. 3 2 4 + + _____ + Energy. [1] 2He 1H 2He SECTION II (40 Marks) Attempt any four questions from this Section Question 5 (a) The diagram given below shows a uniform meter rule being balanced on a knife edge placed at the 40 cm mark, by suspending a weight 50 gf at the mark 20 cm, find: (i) The weight of meter rule. [1] (ii)The resultant moment and its direction if the weight 50 gf is moved to the mark 10 cm. [1] (iii) The position of another weight of 50 gf to balance the rule in part (ii). [1] (b) Your given four pulleys and three strings. Draw a neat and labeled diagram to use them so as to obtain a maximum mechanical advantage equal to 8. In your diagram mark the directions of load L, effort E and tension in each strand. [3] (c) The bullet of mass 5 g travels with a speed of 500 m/s. If it penetrates a fixed target which offers a constant resistive force of 1000 N to the motion of the bullet, find: (i) The initial kinetic energy of the bullet, (ii) The distance through which the bullet has penetrated before coming to rest, and (iii) The speed with which the bullet emerges out of the target if target is of thickness 0.5 m. Question 6 (a) Orange light of wavelength 6000 A travelling in air gets refracted in water. If the speed of light in air is 3x108 m/s and refractive index of water is 4/3, find : (i) the frequency of light in air, (ii) the speed of light in water, and (iii) the wavelength of light in water. [2] (b) A ray of light PQ is incident normally on the face AB of an equilateral glass prism. Complete the ray diagram showing its emergence into air after passing through the prism. Critical angle of the glass is 42 . [3] (i) Write the angles of incidence at the faces AB and AC of the prism. (ii) Name the phenomenon which the ray of light suffers at the face AB, AC and BC of the prism. (c) (i) State the factors affecting the angle of deviation. [2] (ii) Define total internal reflection. [1] (ii) Draw i curve. [1] Question 7 (a) (i) Define virtual image. [1] (ii) An object height 3 cm is placed at a distance of 18 cm in front of a convex lens of focal length 6 cm. (i) Find the position and size of image and (ii) state the characteristics of image. [2] (b) The power of lens of a myopic person is 3.75 D. Find the nature and focal length of the lens. Also write the lens formula. [3] (c) Define echo. Two men 1.02 km apart stand at same distance from a vertical hillock. One of them fires a shot and other hears the echo 2 s after hearing the direct sound. Find the distance of the man from the hillock assuming the velocity of sound to be 340 m/s. [4] Question 8 (a) Define specific resistance and state its unit in CGS and SI system. [3] (b) An electric heater is rated 750W-200V. Calculate: [3] (i) Current flowing through it (ii) Resistance of its element (iii) If the heater is used to heat 400 g of water at 20 C and switched on for 2 minutes, calculate the final temperature of water. (SHC of water is 4.2 J/g C) (c) Below figure shows a circuit diagram, containing 8 cells of emf 1.5 V and internal resistance 0.25 . Calculate: [4] (i) Total emf of battery (ii) Total internal resistance (iii) Total external resistance (iv) Current recorded by ammeter (v) Current flowing through 12 resistor (vi) Current flowing through 6 resistor (vii) Potential drop across the terminals of the cell (viii) Potential difference across the parallel combination of resistors. Question 9 (a) (i) Heat supplied to a solid changes into liquid. What is this change in phase called? (ii) During the phase change does the average kinetic energy of the molecules of the substance increase? (iii) What is the energy absorbed during the phase change called? [3] (b) (i) State two differences between Heat capacity and Specific heat capacity . (ii) Give a mathematical relation between Heat capacity and Specific heat capacity.[3] (c) The temperature of 170 g of water at 50 C is lowered to 5 C by adding certain amount of ice to it. Find the mass of ice added. Given: Specific heat capacity of water = 4200 J kg-1 C-1 and specific latent heat of ice = 336000 J kg-1. [4] Question 10 (a) Define radio isotopes. A radioactive substance is oxidized. What changes would you expect to take place in the nature of radioactivity? Explain your answer. [3] (b) Define background radiations. Explain its sources. (c) (i) Uranium nucleus 92U238 undergoes several disintegrations and ultimately decays to lead nucleus 82Pb206. How many alpha and beta particles are emitted? (ii) State one difference and one similarity between a beta particle and an electron. [4]
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