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Shri Vile Parle Kelavani Mandal s C.N.M. School and N.D. Parkeh Pre-primary School Std: X MUST KNOW QUESTIONS (PHYSICS) 2016-17 Question 1: i. Differentiate between: (a) contact and noncontact forces. (b) centripetal and centrifugal force. ii. State the general character of non-contact forces. iii. State the factors affecting the turning point of a body. iv. State the conditions necessary for a body to be in equilibrium. v. Can the moment of force be zero even if force is not zero? If so, when ? vi. Derive the relation between newton and dyne. vii. Define: (a) C.G. (b) moment of force. (c) force. viii. A uniform meter scale balances horizontally on a knife-edge placed at 55 cm mark when a mass of 25 g is suspended from one end. Draw a diagram of this arrangement. Calculate the mass of the scale. ix. What is the position of C.G. of: (a) circular disc. (b) hollow cone (c) triangular lamina. x. A spanner has a long handle. Why? Question 2: i. Differentiate between: (a) work and power.(b) kinetic and potential energy.(c) renewable and non renewable energy. ii. Derive relation between joule and erg. iii. The work done by a fielder when he takes a catch in a cricket match, is negative. Explain. iv. A pump is used to lift 500 kg of water from the depth of 80 m in 10 s. Calculate: (a) the work done by the pump (b) the power at which the pump works (c) the power rating of the pump if its efficiency is 40% (g = 10 ms -2). ________________________________________________________________________________________________________ Std: X Physics page 1 v. A body of mass 5 kg falls from a height of 10 m to 4 m. Calculate the: (a) loss in potential energy of the body (b) total energy possessed by the body at any instant? (g = 10 ms -2) vi. A force of 15 N required to pull up a body of mass 2 kg through a distance of 5 m along an inclined plane making an angle of 30o with the horizontal is shown in the diagram below: 5m B 15 N C 30o A mg Calculate: (a) work done by the force in pulling the body (b) the force due to gravity on the body (c) the work against the force due to gravity (g = 9.8 m s-2) (d) Account for the difference in the answers of part (i) and part (iii). vii. A simple pendulum is set in motion. Observe the diagram and answer the following questions: (a) Name the position A, B or C when kinetic energy is maximum and potential energy is zero. (b) Name the position A, B or C when kinetic energy is zero and potential energy is maximum. (c) State the law of conservation of energy. viii. A force F acts on a body and displaces it by a distance S, making an angle with the direction of force. (a) Write the expression for the work done by the force. (b) What should be the angle between force and displacement to get: (i) zero work (ii) maximum work? ________________________________________________________________________________________________________ Std: X Physics page 2 ix. If the power of a motor is 40 kW, then with what speed can it lift a load of 20, 000 N. x. Though wood is a renewable source of energy it is not advisable to use wood as a source of energy. Why? xi. State the limitations of using wind energy. xii. Give the energy degradation while cooking food and while running of a vehicle. xiii. A light mass and a heavy mass have equal momentum. Which will have more kinetic energy? Why? xiv. Which physical quantity does the unit electron volt (e V) measure? How is it related to the S.I. unit of this quantity? Question 3: i. Draw a ray diagram to show that the apparent depth of water in a pond is less than its real depth. ii. Differentiate between real image and virtual image. iii. Define: (a) critical angle (b) total internal reflection. iv. State the conditions necessary for total internal reflection to take place. v. State the factors on which the deviation produced by a prism depends. vi. A long rod of length 100 cm has its fulcrum situated at a distance of 10 cm from the load. Calculate M.A. of the rod. vii. Mention two properties of wave, one which varies and the other which remains constant when the wave passes from one medium to another. viii. Why does the earth appear blue to an astronaut in space? ix. A lens is used to produce a virtual, erect and diminished image of an object. Name the type of lens and draw a ray diagram for the same. x. Differentiate: Reflection of light from a plane mirror and total internal reflection of light from a prism. xi. Name any two electromagnetic waves which have frequency higher than that of violet light. State one use of each. xii. Explain why infrared radiations are used for photography in fog. xiii. State the factors on which the focal length of a lens depends. ________________________________________________________________________________________________________ Std: X Physics page 3 Question 4: i. Draw a neat labeled diagram using four pulleys and three strings to obtain a M.A. equal to8. Mark the tensions in the strings, position of load and effort. ii. A gear system has one wheel with 10 teeth and the other with 40 teeth. Calculate the gain in speed and gain in torque. iii. The inclined plane should be less steeper in order to increase the M.A. of the plane. Explain. iv. Draw a diagram of a block and tackle system of pulleys having V.R. 5. Indicate the load(L), effort(E) and tension(T). v. Define M.A, V.R. and efficiency of a machine. Give the relation between them. vi. Why does the Class II lever have M.A. less than 1? vii. Explain why scissors for cutting cloth have blades longer than the handles but shears for cutting metals have short blades and long handles? viii. In the block and tackle system, a load of 7.5 kgf is raised with an effort of 2.5 kgf. If there are 4 pulleys in the system, find M.A, V.R and efficiency. Question 5: (i) State the principle on which a D.C. motor works. (ii) On what factors does the magnitude of an induced E.M.F. depend? (iii) What is an electromagnet? (iv) State two ways by which the strength of an electromagnet can be increased. (v) The diagram given below shows two straight wires carrying current. Copy the diagram and draw the pattern of lines of force around them showing their directions. A K B (vi) What is the function of split rings in a D.C. motor? (vii) State two ways of increasing the speed of rotation of a D.C. motor. ________________________________________________________________________________________________________ Std: X Physics page 4 (viii) State Fleming s right / left hand rule. (ix) State Faraday s laws of electromagnetic induction. (x) Distinguish between the primary coil and secondary coil of a step-up transformer. (xi) State two uses of a step-down transformer. (xii) State the principle of a transformer. (xiii) (a) Draw a labeled diagram of the device you would use to transform 200 V A.C. to 15 V A.C. (b) What is the name of this device? (xiv) Give three uses of an electromagnet. (xv) Draw a neat and labeled diagram of an A.C.generator. (xvi) State three differences between the step-up and step-down transformer. (xvii) State the rule used to determine the direction of a: (a) magnetic field produced around a straight current-carrying conductor. (b) force experienced by a current-carrying conductor placed vertically in a magnetic field. (c) current induced in a coil due to its rotation in a magnetic field. (xviii) Solve: (a) A transformer has 1200 turns in its primary coil. If an input of 200 V produces an 11Voutput, then find the number of turns in the secondary coil. (b) In a step-up transformer, the ratio of the number turns in the primary and secondary coils is 1 : 10. What voltage will develop in secondary coil if the primary coil is connected to 220 V? Question 6: (i) Define: (a) Thermionic emission (b) Work function (threshold energy) (c) Properties of a substance to be used as a good thermionic emitter. (d) Radioactivity ________________________________________________________________________________________________________ Std: X Physics page 5 (ii) How many alpha and beta particles are emitted when uranium nucleus 238 92 U decays to 206 82 Pb ? (iii) Copy and complete the following nuclear reactions: Na Mg 01 U Th .......... energy (a) 24 11 (b) 238 92 234 90 (iv) State briefly two uses of a cathode ray tube. (v) Mention two possible sources of background radiations. (vi) State two common properties of gamma radiations and visible light. (vii) Mention two precautions to be taken while handling radioactive materials. (viii) A certain radioactive nucleus emits a particle that leaves it unchanged but increases its atomic number by one. Identify the particle and write its symbol. (ix) Mention one use and one harmful effect of radioactivity. (x) (a) When does the nucleus of an element become radioactive? (b) How is the radioactivity of an element affected when it undergoes a chemical change to form a chemical compound? (xi) Name the three main parts of CRT. Mention one important function of each of the part. (xii) State three properties common to both beta rays and cathode rays. (xiii) What happens to the atomic number and mass number of an element when it emits: (a) an alpha particle (b) a beta particle (c) a gamma radiation (xiv) In a cathode ray tube, why is the: (a) filament made of tungsten? (b) cathode plate coated with oxide of barium or strontium? (c) thick glass screen coated with barium platinocyanide? (xv) Distinguish between alpha, beta and gamma radiations on the basis of: Ionization, penetrating power, stopping substance. (xvi) State what happens when the: (a) filament current increases ________________________________________________________________________________________________________ Std: X Physics page 6 (b) accelerating potential on the anode increases. (c) negative potential on the grid varies. (xvii) What is the principle of a hot cathode ray tube? (xviii) State the three important measures to be taken in a nuclear power plant. (xix) State three uses of radioactivity each in the field of: medical, industry and science. (xx) An atomic nucleus A is composed of 84 protons and 128 neutrons. (a) The nucleus A emits an alpha particle and is transformed into a nucleus B. What is the composition of the nucleus B? (b) The nucleus B emits a beta particle and is transformed into a nucleus C. What is the composition of the nucleus C? Question 7: (i) Define one kilo-calorie of heat. (ii) Differentiate between heat and temperature. (iii) How is heat capacity of a body related to specific heat capacity? (iv) Name a liquid which has the highest specific heat capacity. Write the value. (v) The base of a cooking pan made thick and heavy. Explain. (vi) State the effect of presence of impurity on the melting point of ice. Give one use of it. (vii) It is difficult to cook vegetables on hills and mountains. Explain. (viii) (a) Name the characteristic of sound which enables a person to differentiate with equal loudness but having different frequencies. (b) Define the characteristic named by you in (a). (ix) A radar is able to detect the reflected waves from an enemy aero plane, after a time interval of 0.02 millisecond. If the velocity of the wave is 3 x 10 8 ms-1, calculate the distance of the plane from the radar. (x) The ratio of the amplitudes of two waves is 4 : 9. What is the ratio of their intensities? (xi) Define global warming and green house effect (xii) 2 Ways to minimize in each (i) Technological measures (ii) Economic measures (iii) Policy measures ________________________________________________________________________________________________________ Std: X Physics page 7 (xiii) Define echo and give any one condition to hear an echo distinctly. Give any two uses of echo. (xiv) Distinguish between free vibrations and damped vibrations. (xv) Distinguish between free vibrations and forced vibrations. (xvi) Distinguish between forced vibrations and resonant vibrations. (xvii) State any 2 factors affecting loudness. (xviii) Define pitch and quality. (xix) Distinguish between music and noise. (xx) (a) Which requires more heat: 1g ice at 0 C or 1 g water at 0 C to raise its temperature to 10 C? (b) Explain your answer in part (a) (xxi) A cube of ice of mass 30 g at 0 C is dropped into 200 g of water at 30 C. Calculate the final temperature of water when the whole ice cube has melted. (xxii) An electric heater of power 1000 W raises the temperature of 5 kg of a liquid from 25 C to 31 C, in 2 minutes. Calculate: (a) heat capacity (b) specific heat capacity (xxiii) What do you mean by the following statements: (a) the heat capacity of a body is 50 J K-1 (b) the specific heat capacity of copper is 0.4 J g -1 K-1 (xxiv) (a) Sound made in front of a tall building 18 m away is repeated. Name the phenomenon and explain it. (b) A tuning fork held over an air column of a given length, produces a distinct audible sound. What do you call this phenomenon? How does it occur? (xxv) (a) A person is tuning his radio set to a particular station. What is the person trying to do to tune it? (b) Name the phenomenon involved, in tuning of radio set. (c) Define the phenomenon named by you in part (b). (xxvi) (a) Name the type of waves which are used for sound ranging. (b) Are these waves mentioned in (i) above, audible to us? Explain. (c) Give one use of sound ranging. ________________________________________________________________________________________________________ Std: X Physics page 8 (xxvii) Observe the following figure and answer the questions that follow: Support B A D C When the pendulum A is set into vibration perpendicular to the length of the support; (a) What happens to the pendulums B, C and D? (b) Which pendulum/s vibrate/s under forced vibration? (c) Which pendulum/s vibrate/s under resonance? (xxviii) Explain the factors on which the frequency of a vibrating string depends. Question 8: (i) (a) Define Potential Difference (b) Explain the factors affecting the resistance of a conductor. (ii) (a) State Ohm s law (b) State the limitations of Ohm s law. (iii) (a) Distinguish between parallel and series combination of resistors. (b) In the circuit shown below, calculate the value of x if the equivalent resistance between A and B is 4 . 4 A x 8 B 5 ________________________________________________________________________________________________________ Std: X Physics page 9 (c) State advantages of connecting the appliance in parallel. (d) State disadvantages of connecting the appliance in series. (iv) (a) State the commercial unit of electrical energy and write its relation with S.I. unit of the same. (b) An electric bulb is rated as 100 W, 250 V . What information does this convey? (v) (a) What is a fuse? (b) The earth pin is thicker and longer than other two wires . Explain. (vi) A power circuit uses a cable having three different wires. (a) Name the three wires of the cable. (b) Which of the two wires are at the same potential? (c) To which wire should the metal case of the geyser be connected? (d) To which wire should the switch and fuse be connected? (vii) Draw a diagram to show the transmission of electricity from power generating station to various industries and consumers. (viii) Draw the circuit diagram of a dual control switch, showing the one ON position and OFF position. (ix) Give the new colour coding of wires in cable. (x) State two characteristics of a high tension wire. (xi) A geyser is rated 2 kV A, 240 V. (a) What is the electrical energy consumed by it in (i) kWh, and (ii) J if it is used for 90 minutes. (b) If the cost of electricity is 4.50/ commercial unit, find the cost. (xii) An electric kettle is rated 2.5 kW, 250 V. Find the cost of running the kettle for two hours at 5.40/ unit. (xiii) A voltage source sends a current 2.5 A to a resistor of 20 connected across it for 5 minutes. Calculate: (a) the p.d. of the source (b) the electrical energy supplied by the source, and (c) the heat in calorie, produced in the resistor. ________________________________________________________________________________________________________ Std: X Physics page 10
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