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F.M 80 Tim e 2 Hrs HALF-YEARLY EXAMINATION 2018-2019 SUBJECT: Physics (SCIENCE Paper 1) 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. Section I is compulsory. Attempt 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) How much work is done by a coolie carrying a load on his head and moving on a frictionless horizontal surface. State reasons. [2] b) Fill in the blanks(Do not copy): (i) In a domestic electric circuit, the potential differences between the live and neutral wire is __________________. (ii) Resistors of 2 , 4 and 6 are connected in parallel combination. The ratio of potential difference across them is _____________. [2] c) Calculate the heat capacity of a metal block of mass 500g if 2000J of heat raises its temperature from 323K to 423K. [2] d) A radioactive substance is oxidized. What changes are expected to occur in its nature of radioactivity? Explain your answer. [2] e) A guitarist tightens the strings of the guitar before playing. What parameter is he changing? What subjective property of sound change with this? [2] Question 2 a) Give the energy transformations of the following: [2] (i) An arrow shot from a bow (ii) A microphone in use b) For the same angle of incidence, the angles of refraction in three different media A, B and C are 15O, 25O and 30O respectively. In which medium, the speed of light be minimum and why? [2] c) What is electron volt? How is it related to the SI unit of energy? [2] d) State the factors affecting loudness and pitch of a sound. [2] e) A uniform metal wire has resistance of 80 . It is cut into four equal lengths. Find the equivalent resistance when three parts are connected in series and fourth in parallel. [2] 1 Question 3 a) Define centre of gravity and centripetal force. [2] O O b) Which of the two, 1g ice at 0 C or 1g water at 0 C contains more heat? Give reasons. [2] c) To use a machine as a force multiplier, which class of lever should be preferred? Sketch the class of lever. [2] d) Why is the handle of a grinding stone of a hand flour-grinder placed near the rim of the stone? [2] e) An electric iron rated 750W-230V. Calculate the electrical energy consumed by it in 12 hours. If the cost of electricity is `5 per unit, calculate the total cost. [2] Question 4 a) State two conditions for a body acted upon by several forces to be in equilibrium. b) A convex lens forms an image of an object equal to the size of the object. (i) Where is the object placed in front of the lens? (ii) Draw a diagram to illustrate it. c) State the conditions required for total internal reflection. d) Copy the diagram given below and complete the path of light ray till it emerges out of the prism. The critical angle of the prism is 42O. In your diagram, mark the angles wherever necessary. [2] [2] [2] [2] e) Calculate the mass of ice required to lower the temperature of 300g of water at 40 OC to water at 0OC. (Specific latent heat of ice=336J/g. Specific heat capacity of water=4.2J/g OC). [2] SECTION II (40 Marks) Attempt any four questions from this Section. Question 5 a) A uniform meter scale can be balanced at the 70cm mark when a mass of 0.05kg is hung from the 94cm mark. [3] (i) Draw a diagram of the arrangement. (ii) Find the mass of the metre scale. b) Calculate power of engine required to lift 105kg of coal in 1 hour from a mine 360m deep. [g=10m/s 2].[3] c) A pulley system with VR=4 is used to lift a load of175kgf through a vertical height of 15m. The effort required is 150kgf in downward direction. (g=10m/s 2). Calculate: [4] (i) Distance moved by the effort. (ii) Work done by the effort (iii) MA of the system (iv) Efficiency of the system Question 6 a) (i) A coin is placed at the bottom of a beaker appears to be raised by 4cm. If the refractive index of water is 4/3, find the depth of the water in the beaker. (ii) A ray of light is incident as a normal on the surface of separation of two different mediums. What is the value of angle of incidence in this case. [3] b) (i) Power of a lens is +2D. What is the focal length of the lens? Whether it is a concave or a convex lens? (ii) Relate angle of deviation with angle of emergence for minimum deviation through a prism. [3] 2 c) An object of height 4cm is placed at a distance 24cm in front of a convex lens of focal length 8cm. (i) Find the position and size of the image (ii) State the characteristics of the image. (iii) Draw the ray diagram for the above condition. [4] Question 7 a) A man fires a gun and hears its echo after 5s. The man then moves 310m towards the hill and fires his gun again and hears the echo after 3s, calculate the speed of sound. [3] b) A vibrating tuning fork is placed over the mouth of a burette filled with water. The tap of the burette is opened and the water level gradually starts falling. It is found that the sound from the tuning fork becomes very loud for a particular length of the water column. (i) Name the phenomenon taking place when this happens. (ii) Why does the sound becomes very loud for this length of the water column. [3] c) Give reasons for the following: [4] (i) Soldiers are asked to break their footsteps while crossing a suspension bridge. (ii) Musical sound for some could mean noise for others. Question 8 a) The following is a heating curve for ice. Answer the following questions referring the graph: [3] (i) What does AB and CD represents? (ii) What conclusion can you draw as regards the nature of ice from the above graph? b) A piece of lead at 120OC is dropped in 50g of cold water contained in a copper calorimeter of mass 100g at 20OC such that resultant temperature of mixture is 60 OC. Find the mass of lead used. [SHC of water=4200Jkg-1K-1, SHC of copper=400 Jkg-1K-1, SHC of lead=500 Jkg-1K-1] [3] c) (i) It is advisable to pour cold water over burns caused by hot solids in human body. Why? (ii) Heat energy is supplied at a constant rate to 100g of ice at 0 OC. The ice is converted into water at 0 OC in 2minutes. How much time will be required to raise the temperature of water from 0 OC to 20OC. [SHC of water=4.2Jg-1K-1, SLH of ice= 336Jg-1] [4] Question 9 a) (i) State Ohm s law. (ii) A metal wire of resistance 6 is stretched so that its length is increased to thrice its original length. Calculate its new resistance. [3] b) (i) An electrical gadget can give an electric shock to its users under certain circumstances. Mention any two of these circumstances. (ii) What preventive measure provided in a gadget can protect a person from an electric shock. [3] c) The given figure shows a circuit: 3 When the circuit is switched on, the ammeter reads 0.5A. (i) Calculate the value of the unknown resistor R. (ii) Calculate the charge passing through the 3 resistor in 120s. (iii) Calculate the power dissipated in the 3 resistor. [4] Question 10 a) Define radio-isotopes. State one use and one harmful effect of radio-isotopes. [3] b) Complete the following nuclear reaction using suitable subscripts and superscripts wherever missing:[3] 235 + 0n1 __ Ba148 + 36Kr ----- + ------- 0n1 92U c) Radiations given out from a source when subjected to an electric field to n direction perpendicular to their path arc shown below in the diagram. The arrows show the path of the radiation A, B and C. Answer the following questions in terms of A, B and C. [4] (i) Name the radiation B which is unaffected by the electrostatic field. (ii) Why does the radiation C deflect more than A? (iii) Which among the three causes the least biological damage externally? (iv) Name the radiation which is used in carbon dating. 4 5
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