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Le Grand International School Pre Board I Physics Class-X Time Allowed: 2 hours Maximum Marks: 80 General Instructions: Answers to this Paper must be written on the paper provided separately. You will not be allowed to write during 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. Section A is compulsory. Attempt any four questions from Section B. The intended marks for questions or parts of questions are given in brackets [ ]. Section A 1. Choose the correct answers to the questions from the given options. (Do not copy the question, write the [15] correct answers only.) (a) (b) (c) Study the diagram alongside and calculate the moment of couple. a) 1 Nm b) 6 Nm c) 2 Nm d) 4 Nm When white light is dispersed by a prism, compared with blue light, the red light is a) slowed down less and refracted less b) slowed down more and refracted less c) slowed down more and refracted more d) slowed down less and refracted more A pendulum is oscillating freely. Its bob has: a) a constant energy which is the sum of [1] [1] [1] b) only kinetic energy potential and kinetic energy c) maximum kinetic energy at extreme position (d) (e) d) maximum potential energy at its mean position A radioactive substance emits: [1] a) in the order of , and particles b) -radiations or -radiations c) simultaneously , and radiations d) X-rays and -rays Assertion (A): When a force acts on a stationary rigid body which is free to move and if body starts moving in straight path in direction of applied force, then it is said to be linear motion. [1] Reason (R): If free body is acted upon by two unequal forces in opposite direction, but not in one line, the effect is that the body will possess rotational motion only. a) Both A and R are true and R is the b) Both A and R are true but R is not the correct explanation of A. correct explanation of A. c) A is true but R is false. (f) d) A is false but R is true. The point on the principal axis of a convex lens, such that rays of light starting from it on passing [1] through the lens, move parallel to the principal axis is called: (g) (h) (i) a) first focal point b) second focal point c) aperture of lens d) optical centre For hearing an echo, the minimum distance between the source of sound and reflecting body should be a) 24 m b) 12 m c) 17 m d) 51 m The voice of women is shrill as compared to men because of the difference in their: a) loudness b) speed c) all of these d) frequency The current flowing through a resistor connected in an electric circuit and the potential difference [1] [1] [1] applied across its ends are shown in figure below. The value of the resistance of the resistor is A (j) V a) 10 b) 8 c) 5 d) 1 By reversing the direction of current in an electromagnet, the magnetic field produced by it a) remains unchanged in strength and b) [1] gets reversed in direction direction c) decreases in strength d) increases in strength (k) A nut can be opened by a lever of length 0.25 m by applying a force of 80 N. What should be the length [1] of lever, if a force of 32 N is enough to open the nut? a) 0.18 m (l) (m) c) 3.0 m The specific heat capacity of water in S.I. system is: b) 1.5 m d) 0.625 m [1] a)42 JKg-1 K-1 b) 4200 JKg-1 k-1 c) 4.2 Jkg-1 K-1 d) 420 JKg-1 K-1 How many grams of ice at -14oC are needed to cool 200 g of water from 25oC to 10oC? (Take, specific heat of ice = 0.5 cal g-1 oC-1 and latent heat of ice = 80 cal g-1) [1] (n) a) 27 g b) 31 g c) 20 g d) 30 g [1] A coin is placed at a depth of 15 cm in a beaker containing water. The refractive index of water is 4/3, calculate height through which the image of the coin is raised. (o) a) 0.75 cm b) 1.75 cm c) 3.75 cm d) 2.75 cm The critical angle for a material X is 45o. The total internal reflection will take place, if the angle of [1] incidence in the denser medium is: 2. a) more than 45o, but not 90o b) 90o c) less than 45o, but not zero degree d) less than 45o Answer the following questions: (a) i. Name a machine which can be used to [15] [1] i. Multiply force. ii. Change the direction of force applied. ii. If a machine is used to lift a load of 50 N such that resistance due to friction and movable part of [1] machine is 15 N, then the total lifted load is 65 N, i.e., (50 + 15) N. If the displacement is caused through 2 m, then find actual and useful output. iii. [1] Diagram given in below is representing a pulley system having a velocity ratio 3 and an efficiency of 80%. Calculate the mechanical advantage and efficiency. [2] (b) Draw a neat labelled diagram for a particle moving in a circular path with a constant speed. In your [2] diagram, show the direction of velocity at any instant. (c) The diagram below shows a claw hammer used to remove a nail: [2] i. To which class of lever does it belong? ii. Give one more example of the same class of lever mentioned by you in (i) for which the mechanical advantage is greater than 1. (d) When a body is placed on a table top, it exerts a force equal to its weight downwards on the table top but does not move or fall. i. Name the force exerted by the table top. ii. What is the direction of the force? (e) Two bodies, A and B of equal mass are kept at heights 20 m and 30 m respectively. Calculate the ratio of [2] their potential energies. 3. (f) Calculate the work done in moving a charge of 4 C from a point at 220 V to a point at 230 V. [2] (g) State two differences between light waves and sound waves. [2] Answer the following questions; (a) [10] [2] i. Define the power of a lens. ii. A lens has focal length 25 cm. Calculate the power of lens. (b) Calculate the effective resistance across AB: [2] (c) (d) How many protons will constitute a charge of 1 C? [2] i. Give one example, where high specific heat capacity of water is used as a heat reservoir. [2] ii. Give one example, where high specific heat capacity of water is used for cooling purposes. [2] iii. Show by equations, the effect on the proton number Z and mass number A of the parent nucleusbrought about by the two types of radioactive decay. Section B Attempt any 4 questions 4. Answer the following questions: (a) [10] Explain the meaning of reversibility of light. (b) [3] i. Define calorimetry. [3] ii. Name the material used for making a Calorimeter. iii. Why is a Calorimeter made up of thin sheets of the above material answered in (ii)? 5. (c) If the speed of light in air is 3 108 ms-1, determine the speed of light in glass. The refractive index of glass of 1.5. Answer the following questions: (a) A ray of monochromatic light is incident from air on a glass slab. [4] [10] [3] i. Draw a labelled ray diagram showing the change in the path of the ray till it emerges from the glass slab. ii. Name the two rays that are parallel to each other. iii. Mark the lateral displacement in your diagram. (b) i. If a monochromatic beam of light, undergoes minimum deviation through an equiangular prism,how does the beam pass through the prism, with respect to its base? [3] ii. If white light is used in the same way as in (i) above, what change is expected in the emergent beam? (c) Jatin puts a pencil into a glass container having water and is surprised to see the pencil in a different [4] state. i. What change is observed in the appearance of the pencil? ii. Name the phenomenon responsible for the change. iii. Draw a ray diagram showing how the eyes sees the pencil. 6. Answer the following questions: (a) [10] State the class of lever to which each one of the following items belongs. Also give the relative [3] position of load (L), effort (E), and fulcrum (F) in each case i. Sea-saw ii. Knife iii. Nut cracker (b) i. With reference to the direction of action, how does a centripetal force differ from a centrifugal [3] force during uniform circular motion? ii. Is centrifugal force the force of reaction of centripetal force? iii. Compare the magnitudes of centripetal and centrifugal force. (c) [4] If a man raises a box of 50 kg mass to a height of 2 m, while the other man raises the same box to a same height in 5 min. Compare i. the work done. ii. the power developed by them. 7. Answer the following questions: (a) [10] A person standing between two vertical cliffs and 480 m from the nearest cliff shouts. He hears the first [3] echo after 3 s and the second echo 2 s later. Calculate: i. The speed of sound. ii. The distance of the other cliff from the person. (b) Arrange , and rays in ascending order with respect to their [3] i. Penetrating power. ii. Ionising power. (c) iii. Biological effect. [4] i. Name the phenomenon involved in tuning a radio set to a particular station. ii. Define the phenomenon named by you in part (i) above. iii. What do you understand by loudness of sound? iv. In which units is the loudness of sound measured? 8. Answer the following questions: (a) [10] i. Write one advantage of connecting electrical appliances in parallel combination. [3] ii. What characteristics should a fuse wire have? iii. Which wire in a power circuit is connected to the metallic body of the appliance? (b) The ore of Uranium found in nature contains 238 U and 235 U. Although both the isotopes are 92 92 fissionable, it is found out experimentally that one of the two isotopes is more easily fissionable. [3] i. Name the isotope of Uranium which is easily fissionable. ii. Give a reason for your answer. iii. Write a nuclear reaction when Uranium 238 emits an alpha particle to form a Thorium (Th) nucleus. (c) [4] Two resistor of 4 and 6 are connected in parallel to a cell to draw 0.5 A current from the cell. i. Draw a labelled circuit diagram showing the above arrangement. ii. Calculate the current in each resistor. 9. Answer the following questions: (a) i. Write an expression for the heat energy liberated by a hot body. [10] [3] ii. Some heat is provided to a body to raise its temperature by 25 C. What will be the corresponding rise in temperature of the body as shown on the Kelvin scale? iii. What happens to the average kinetic energy of the molecules as ice melts at 0 C? (b) Some ice is heated at a constant rate, and its temperature is recorded after every few seconds, till [3] steam is formed at 100 C. Draw a temperature time graph to represent the change. Label the two phase changes in your graph. (c) The diagram below shows a point source P inside a water container. Four rays A, B, C, D starting from the source P are shown upto the water surface. (i) Show in the diagram the path of these rays after striking the water surface. The Critical Angle for water air surface is 48 . (ii) Name the phenomenon which the rays B and D exhibit. [4]
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