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Half yearly Examination: 2018 Class: 10 SCIENCE Paper 1(PHYSICS) Time: 2 hrs. Max.marks: 80 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 answer. Section 1 is compulsory. Attempt any four questions from section 2. The intended marks for questions or parts of question are given in ( ) Section 1 Question 1: [5 Questions 2=10] a) Name the force required for uniform circular motion .State its direction. b) State factors on which the position of centre of gravity of a body depend. Explain with example. c) A body is acted upon by a force .State two conditions when the work is zero. d) A machine works as a (1) force multiplier (2) speed multiplier. In each case whether the velocity ratio is more than or less than 1. e) For which colour of white light, is the refractive index of a transparent medium (1) the least (2) the most? Question 2: [5 Questions 2=10] -2 a) How fast a man weighing 600N run so that his kinetic energy is 750 J .( g = 10ms ) b) A force of 5 kgf is required to cut a metal sheet .A shears used for cutting the metal sheet has its blades 5 cm long, while its handles are 10 cm long. What effort is needed to cut the metal; sheet? c) The refractive index of water is 4/3 and of glass is 3/2.What is the refractive index of glass with respect to water? d) Express the power (with sign) of a concave lens of focal length 20 cm. e) The wavelength of X rays is 0.01 A. Calculate its frequency. State the assumption made, if any. Question 3: [5 Questions 2=10] a) Explain the term critical angle with the aid of labelled diagram. b) What is lateral displacement? Draw a ray diagram showing the lateral displacement of a ray of light when it passes through a parallel sided glass slab. c) State the condition for each of the following; I. A lens has both its focal lengths equal II. A ray passes undeviated through the lens. d) A concave lens forms the image of an object kept at a distance of 20 cm in front of it,at a distance 10 cm on the side of the object.(1) What is the nature of the image? (2)Find the focal length of lens? e) Draw a neat labelled ray diagram to show the formation of image by a magnifying glass. State three characteristics of the image. Question 4: [5 Questions 2=10] a) What is the range of wavelength of the spectrum of white light in (1) A (2) nm? b) Name one electromagnetic wave of wavelength smaller than that of violet light. State its one use. c) What should be the minimum distance between the source and reflector in water so that the echo is heard distinctly? The speed of sound in water is 1400 ms-1. d) Name the unit used to measure the sound level. e) State the factor that determines pitch of a note and the loudness of the sound heard. Section 2 Question 5: [4+3+3=10] a) The wheel shown in the diagram has a fixed axle passing through O The wheel is kept stationary under the action of (i) a horizontal force F1 at A and (ii) a vertical force F2 at B. 1) Show the direction of force F2 in the diagram. 2) Which of the force F1 or F2 is greater? 3) Find the ratio between the forces F1 and F2.Given: AO = 2.5cm, BO = 1.5 cm and O O = 2 cm. b) Show that the sum of kinetic energy and potential energy i.e. total mechanical energy is always conserved in the case of freely falling body under gravity from a height h by finding it when (i) the body is at top (ii) the body has fallen a distance x,(iii) the body has reached the ground. Neglect air resistance. -1 c) A body of mass 50 kg has a momentum of 3000Kgms .Calculate the kinetic energy and velocity of the body. Question 6: [4+3+3=10] a) The diagram shows an arrangement of three pulleys A,B and C.The load is marked L and effort as E. 1) Name the pulleys A ,B and C. 2) Mark in the diagram the directions of load L, effort E and tensions T1 and T2 in the two strings. 3) How are the magnitudes of L and E related to the tension T1? 4) Calculate the mechanical advantage and velocity ratio of the arrangement. 5) What assumption have you made in parts (3) and (4). b) A truck weighing 1000 kgf changes its speed from 36 km/h to 72 km/h in 2 minutes .Calculate the work done by the engine and its power. c) Figure shows a lemon crusher 1) In the diagram, mark the position of the fulcrum and the line of action of load L and effort E. 2) Name the class of lever. Question 7: [4+3+3=10] a) The diagram below shows a glass block suspended in the liquid. A beam of light of single colour is incident from liquid on one side of the block. 1) Draw diagrams to show how does the light ray bend when it travels from liquid to glass and then to liquid if (i) the light slows down in the glass, and (ii) the light speeds up in the glass. 2) State two conditions under which the light ray passing from liquid to glass travels straight without bending. Will the glass be visible then. b) What is a total reflecting prism? State three actions that it can produce. Draw a ray diagram to show one such action of the total reflecting prisms. c) A ray of light enters a glass slab PQRS as shown in the diagram. The critical angle of glass is 42 .Copy this diagram and complete the path of the ray till it emerges from the glass slab. Mark the angle in the diagram wherever necessary. Angle QPS is right angle. Question 8: [4+3+3=10] a) The diagram shows the experimental setup for the determination of focal length of lens using a plane mirror. 1) Draw two rays from the point O of the object to show the formation of image I at O itself. 2) What is the size of image? 3) State two more characteristics of the image I. 4) Name the distance of the object O from the optical centre of the lens. b) The diagram below shows a ray of light PQ coming from an object P and incident on the surface of the thick glass plane mirror .Copy the diagram and complete it to show the formation of three images of the object P as formed by the mirror. Which image will be brightest? c) Define the term principal foci of a concave lens and show them with the help of proper diagram. Question 9: [4+3+3=10] a) Give two properties of ultraviolet radiations and infrared radiations which differ from the visible light. b) A convex lens forms an image 16 cm long of an object 4 cm long kept at a distance 6 cm from the lens.The object and image are in the same side of the lens. 1) What is the nature of image? 2) Find the position of the image and the focal length of lens. c) Define the term dispersion of light and explain the cause of dispersion of white light through a prism. Question 10: [4+3+3=10] a) The diagram shows the displacement time graph of a vibrating body. 1) Name the kind of vibrations. 2) Give one example of such vibrations. 3) Why is the amplitude of vibrations gradually decreasing? 4) What happens to the vibrations of the body after some time? b) What is meant by an echo? State two conditions necessary for an echo to be heard distinctly. c) A pendulum has a frequency of 5 vibrations per second. An observer starts the pendulum and fires a gun simultaneously .He hears echo from the cliff after 8 vibrations of the pendulum. If the velocity of sound in air is 340 -1 ms .Find the distance between the cliff and observer.
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