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Cal LOKHANDWALA FOUNDATION SCHOOL PRELIMINARY EXAMINATION - 2020-21 SUBJECT: PHYSICS Date : 15/01/2021 Duration: 2 hrs Grade: 10 Max Marks: 80 __________________________________________________________________________________ General Instructions: This question paper consists of two sections A and B. Section A is compulsory. Attempt any four questions from Section B. This paper consists of 4 printed sides. __________________________________________________________________________________ SECTION A (40 marks) (Attempt all questions from this section) Question 1 a) In a uniform circular motion, the body moves with uniform acceleration. Is this statement true? Explain your answer. (2) b) How much work is needed to be done on a ball of mass 100 g to give it a momentum of 5 kg m/s ? (2) c) A radioactive substance is oxidized. How would the nature of radioactivity be changed ? Explain your answer. (2) d) Name the constituent colour of white light for which i) the deviation produced by the glass prism is the least . ii) the refractive index of glass is maximum. (2) e) State two differences between Forced and Resonant vibrations. (2) Question 2 a) Calculate the power of an engine required to lift 100 kg of coal per hour from a mine 360 m deep ? (Take g= 10 m/s ). (2) b) Name a simple machine which can be used to : i) multiply force ii) only change the direction of force applied. (2) c) 2000 calories of heat is supplied to 100 g of water. Find the rise in temperature. (Take specific heat capacity of water as 1 cal g C .) (2) d) Which is easier to turn: A steering wheel of a large diameter or a steering wheel of a small diameter ? Explain your answer. (2) e) A ray of light enters a glass slab as shown in the figure below. Copy and complete the path of the ray till it emerges out from the slab. Mark the necessary angles in the diagram . (2) Question 3 a) State the conditions required for the total internal reflection of light to take place. (2) P.T.O GRADE:10 SUBJECT:PHYSICS Page:2 b) An electric iron box is rated 220 V,1.5 kW. If the iron is used for 2 hours daily, find the cost of running it for the month of September if the cost of 1 unit is 5. (2) c) An equal amount of heat is supplied to two liquids A and B. The liquid B shows a greater rise in temperature. Which liquid has a greater specific heat capacity if both the liquids have the same mass? Explain your answer. (2) d) What are background radiations? Name its two sources. (2) e) The velocity of light in diamond is 120000 km/s. What is its Refractive Index? (2) Question 4 a) What resistance must be connected to a 12 resistor to provide an effective resistance of 8 ? Explain your answer with the required steps. b) State two advantages of connecting electrical appliances in parallel with the mains. c) An object is placed at a distance of 24 cm in front a convex lens of focal length 8 cm. Find the position of the image . d) State and explain any two factors which affect the resistance of a metallic wire. e) A radar sends a signal to an aeroplane at a distance 4.5 km away with a speed of 3 x 10 m/s. After how long is the signal received back from the aeroplane ? (2) (2) (2) (2) (2) SECTION B (40 marks) (Attempt any four questions from this section) Question 5 a) In the figure given below, AB is the object. i) Name the lens LL . ii) Copy and complete the ray diagram to show the image formation. iii) Write the characteristics of the image formed. b) A hot solid of mass 60 g at 100 C is placed in 150 g of water which is at 20 C. The final steady temperature recorded is 25 C. Calculate the specific heat capacity of the solid. c) Name the radiation which can be detected by i) a thermopile. ii) a solution of silver chloride. d) Why are infrared radiations used for signals during war? P.T.O (3) (3) (2) (2) GRADE:10 SUBJECT:PHYSICS Page:3 Question 6 a) Find the current drawn from the battery by the network of resistors as shown in the figure. (3) b) In a nuclear reaction, a nucleus X which has atomic number 88 and mass number 226 changes to another nucleus Y after emitting two alpha and three beta particles. What is the mass number and atomic number of Y? Represent this change in the form of an equation. c) i) Draw a labeled diagram of a block and tackle system of pulley with two pulleys in each block. Label the direction of the load, effort and the tension in the string. ii) What is the mechanical advantage and velocity ratio of the above system ? d) Kilowatt hour is the unit of which physical quantity? (2) (2) (2) (1) Question 7 a) State two differences between e.m.f. and terminal voltage of a cell. (2) b) A cell of e.m.f 12 V and internal resistance 2.0 is connected to two resistors 4 and 6 joined in series. Calculate the i) current in the circuit ii) voltage drop iii) Potential difference across the 4 resistor. iv)Potential difference across the cell. (4) c) The figure below shows a radioactive source S in a thick lead walled container having a narrow opening. i) Copy and complete the diagram to show the path of , and radiations. ii) Which radiation is deflected the most? Give reason for your answer. P.T.O (4) GRADE: 10 SUBJECT: PHYSICS Page:4 Question 8 a) Four pendulums, A,B, C and D are suspended from the same elastic support as shown in the figure. Pendulums A and C are of the same length. If pendulum A is set into transverse vibrations, i) Which pendulum will vibrate with maximum amplitude? Give reason for your answer. ii) What type of vibrations take place in pendulums B, C and D? (3) b) A uniform metre scale can be balanced at 70 cm mark when a mass of 50 g is hung from 94 cm mark. Draw the diagram of the arrangement and find the mass of the metre scale. (3) c) i) A sound made on the surface of a lake takes 3 s to reach a boatman. How much time will it take to reach a diver inside the water at the same depth? (Velocity of sound in air =330m/s and velocity of sound in water is 1450 m/s) (2) ii) Name the characteristic of sound in relation to its waveform and the characteristic of light in relation to its wavelength. (2) Question 9 a) State the energy conversion taking place in: i) Charging a battery. ii) Microphone (2) b) What is the Work - Energy Theorem? Give the mathematical equation for it. (2) c) Name the device used to protect the electric circuits from overloading and short circuiting. What is the principle on which this device works? (2) d) An electric iron is rated 220 V, 1kW. Under normal conditions, find: i) the resistance of the heating element in the iron. ii) the amount of current that will flow through the element. iii) the amount of heat that will be produced in 5 minutes. iv) the power consumed if the line voltage falls to 180 V. (4) Question 10 a) State two differences between centripetal and centrifugal force. (2) b) A wire of resistance 27 having a length of 30 cm is tripled on itself. What is its new resistance? (2) c) A lens forms an erect, magnified and virtual image of the object. i) Name the lens. ii) Draw a ray diagram to show the image formation. (3) d) The bob of a simple pendulum is imparted a velocity of 4 m/s when it is at mean position. To what maximum vertical height will it rise on reaching its extreme position, if 70% of its energy is lost in overcoming the friction of air? (Take g= 10 m/s ). (3) ----------------------------------------------------
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