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ST. JOHN S UNIVERSAL SCHOOL FIRST PRELIM 2020-2021 Class: X Physics Date :14/10/2020 Time : 2 hours Marks : 80. Answers to this paper must be written on a ruled sheet. First 10 minutes are to be spent in reading the question paper. The time given at the head of this paper is for writing and uploading the paper. The Answer Sheet should have the following details mentioned - Date , Full Name,Class & Div. The pages should be numbered appropriately. Section A All Questions Compulsory Question 1 a. What is the SI unit of i)moment of couple ii) Power [2M] b. State two conditions of equilibrium [2M] c. What is the position of centre of gravity i)solid cone ii)triangular lamina [2M] d. What force provides the necessary centripetal force in the following case: i. motion of planet around sun ii. Stone tied at the end of the string [2M] e. Sate any two functions of Machines. [2M] Question 2 a.State two condition for light to pass as an undeviated ray. [2M] b. State two factors effecting refractive index . [2M] c. State two advantages of reflecting telescope over a plane mirror as reflector . [2M] d. State any two uses of UV rays. [2M] e. State any two application of lenses . [2M] Question 3 a. Define the term power of lens. Name the type of lens whose power is -3.0 D. [2M] b. State any two properties of ultrasonics waves . [2M] c. State any two uses echoes . [2M] d.Define damped vibration and give an example. [2M] e. Which of the wave(A/B) in the following graph represents louder sound and why ? [2M] Question 4 a. Name two safety precautions to be followed while using [2M] electricity b. What is the colour coding of the wire connected to fuse and metallic case of device [2M] c. Find the equivalent resistance of the following circuit, where each resistance is 6 ohms. [2M] d. Where is a Fuse connected in circuit and Why [2M] e. Give two Characteristics of high tension wire [2M] Section B Any four Questions Question 5 a. Define and state factors affecting moment of force [3M] b. Draw a diagram of a block and tackle system of pulleys having a velocity ratio of 4 [3M] c. Derive a relationship between mechanical advantage , velocity ratio and efficiency. State the unit of mechanical advantage. [4M] Question 6 a.Derive an expression for a potential energy of an object at a height above the earth [3M] b. State the condition when work done by force is i)positive ii)negative iii)zero. Give an Example in each case [3M] c.A metal body of mass 4kg is made fall from a height of 10m. Find i)its initial potential energy ii)kinetic energy just before it strikes the ground iii)total at its midpoint iv)What happens to energy if it comes to rest after striking the ground(g=10ms-2). [4M] Question 7 a. Define refraction of light. State two laws of refraction. [3M] b. Show with the help of neat diagram, how a total reflecting prism can be used to rotate through 180. c. Give Reasons: [4M] [3M] i. A crack in a glass vessel often shines like a mirror ii. A sun a seen a few minutes before its sunrise iii. Infrared rays are used as war signals Question 8 a.How will you differentiate between a convex and concave lens i) by touching ii)by looking distant object iii)by looking at printed image? [3M] b. Draw a diagram to show the image formation in a concave lens, when object is placed at finite distance . [3M] c. An object is placed at a distance of 30cm forms an image at a distance of 10cm in front of it. Find i) Focal length i)magnification iii)nature of the image formed by the lens iv) is it a convex/ concave lens ? [4M] Question 9 a. i. Define resonance. [3M] ii.State two difference between free and forced vibrations. b.Draw a displacement time graph for natural vibration and give an example. [3M] c. A man standing 35m away from a cliff produces an sound and receives the reflected sound. Calculate the time after which sound is heard( Velocity of sound =350ms-1).Can the echo be heard by man and explain your answer . [4M] Question 10 a. Define ohm s law .Name the material used for i)standard resistors and ii)heating wire b. Draw a labelled diagram of three pin socket [3M] [3M] c. Find (i)the current in the ammeter (ii)Voltage drop (iii) potential across 9 ohms resistor, for the following circuit? [4M]
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