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Diamond Jubilee High School Preliminary Examination(SET A) Std : X Science Paper I - Physics Date : 18-1-2021 Marks : 80 Time: 2 hr Answer to this Paper must be written on the paper provided separately. You will not be allowed to write during the first 10 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. Attempt all questions from Section A and any four questions from Section B. The intended marks for questions or parts of questions are given in brackets [ ] This paper consists of five sides Section A (40 marks) (All questions are compulsory) Question 1 [10] a) i) Name the physical quantity also measured in kWh. ii)Give the relation between kWh and the SI unit of the quantity mentioned in (i) above. b) Mechanical energy is the sum of two forms of energy A and B. Form A depends on the velocity of the body while form B whenever put to use can be changed only to form A. Identify the forms of Energy. c) Why is a jack screw provided with a long arm? State the formula to support your answer. d) i) What should be the angle between force and displacement to get maximum work? ii) If a body revolves in a circular path under the influence of a force, what is the work done by the force on completing 100 rounds? e) State two factors on which the lateral displacement produced by a glass slab depends? Question 2 [10] a) If the power of a motor is 100 kW, then at what speed can it raise a load of 50000 N? b) i) If a machine is said to be 80% efficient, then where is the remaining energy lost? ii)Calculate the ideal mechanical advantage of a lever in which the effort arm is 60 cm and the load arm is 4 cm. c) Given below is the V-I Graph of a conductor. Identify which type of a conductor it is and give one example of it. Std : 10 Subject : Physics Page : 1 d) In the figure given below, how far will the boy have to be seated so that the resultant moment of force about the center of the see-saw is zero? e) i) Lead has a specific heat capacity of 130 Jkg-1K-1 . Explain the statement. ii) What will be the Heat capacity of a 5 kg block of lead? Question 3 [10] a) Why is the earth pin of a socket made thicker and longer? b) Name the type of single pulley that can act as a force multiplier. State one reason why a pulley is not 100% efficient. c) Is it possible for the Himalayan ranges to completely melt under the scorching sun? Explain your answer. d) A fish in a pond appears to be seen at a depth of 1.5 m from the surface of the pond. How far is the fish from the water surface? (Refractive Index of water with respect to air is 4/3). e) Draw a graph showing the displacement against time for a body executing natural or free vibration (in vacuum). Question 4 [10] a) Why does the smoke appear white? Define the phenomenon related to this. b) The centre of gravity of a boomerang given in the figure alongside lies outside the material of the body. Draw a diagram to show its position. c) What is understood by the term Dispersion of light and what is its cause? d) As a bottle is placed below a running tap of water. As the bottle is getting filled up, what happens to the pitch of the sound? Why? e) State the effects of background radiations on human health and name any one source of background radiations. Section B (40 marks) (Attempt any 4 questions) Question 5 a) i.The equivalent resistance of the following circuit diagram is 4 . Calculate the value of X. [3] . ii. How does the resistance of the conductor vary with increase in its temperature. [1] Std : 10 Subject : Physics Page : 2 b) i. An electric bulb is rated 240 V, 60 W and is working at 100% efficiency. Calculate the resistance of bulb ii. Explain what is safe current limit of an appliance? [2] [1] c) Radioactive radiations were allowed to fall on a photographic plate, placed in an electric field for few seconds. The photographic plate was developed and three distinct spots (A, B and C) were visible. Identify the radiations, responsible for each spot with reasons. [3] Question 6 a) 40 g of water at 600C is poured into a vessel containing 50 g of water at 200C. The final temperature of the mixture is 300C. Taking the specific heat capacity of water as 4.2 Jg-1K-1, Calculate the heat capacity of the vessel. [4] b) Draw a labelled diagram of a block and tackle system of pulleys having a velocity ratio 5 indicating clearly the points of application and directions of load and effort. [3] [1] c) i. State the full form of SONAR. ii. In a SONAR, ultrasonic waves are sent into the sea water and the reflected waves from a sunken ship are received after 2.0 s . If the velocity of waves in sea water is 1450 ms-1 , find the depth of the sunken ship. [2] Question 7 a) A block of mass 30 kg is pulled up a slope, as shown in the diagram with a constant speed, by applying a force of 200 N parallel to the slope. A and B are the initial and final positions of block. [4] i. Calculate the work done by force in moving the block from A and B. ii.Calculate P.E gained by block. iii.Why is the potential energy and the work done not the same? iv. What should be done to reduce the difference between the work done along AB and the potential energy gained by the block? [Take g=10 ms-2] b) A boy whirls a stone tied to a string in a circular motion with uniform speed. i. Name the force responsible for maintaining the circular motion of the stone. [3] Std : 10 Subject : Physics Page : 3 ii. Name one quantity that is variable/changing in the above motion. iii. If the string breaks during the motion, in what direction will the stone move? c) Copy and complete the diagram given below to show the formation of the image of the object AB. Also write the characteristics of the image formed. [3] Question 8 a) i.State the formula to calculate Moment of a couple. ii. Give one example of moment of a couple. iii. The moment of a force of a 5 N about a point is 2 Nm. Calculate the distance of point of application of the force from the point P. [1] [1] b) How fast should a man weighing 600 N run so that his kinetic energy is 750 J? (g=10 ms-1) [3] [2] c) In the given diagram, a narrow beam of white light is incident on a right-angled isosceles prism. The critical angle of the material of prism for yellow colour of white light is 450 . Complete the diagram to show the path of blue, yellow and red colours of white light till they emerge out of the prism. [3] Question 9 a) Name two precautions to be observed while using electricity and electrical appliances. [2] b) What are dual switches? Mention their one main use. [2] c) The diagram above shows a wire stretched over a sonometer. Stems of two vibrating tuning forks A and B are touched to the wooden box of the sonometer. It is observed that the paper rider (a small piece of paper folded and kept at the centre of the wire) present on the wire flies off when the stem of vibrating tuning fork B is touched to the wooden box but the paper rider just vibrates when the stem of vibrating tuning fork A is touched to the wooden box. i. Name the phenomenon when the paper rider flies off. ii. Why does the paper rider fly off when the stem of tuning fork B is touched to the box? [1] [2] Std : 10 Subject : Physics Page : 4 d) Draw a diagram to show the waveforms of a pure note and a musical note, of same pitch and same loudness. [3] Question 10 a) An isotope of Uranium has a mass number 235 and atomic number 92. i. What is the number of electrons in the neutral atom of this isotope? ii. What is the number of neutrons in the nucleus of this isotope? iii. Do all isotopes have the same number of neutrons? iv. Write any one use of this isotope. [4] b) The figure below represents the electromagnet spectrum i. Fill in the missing labels x and y ii. The radiations of the electromagnetic spectrum shown above are arranged from left to right in the decreasing order of _______ and increasing order of ___________. (copy the sentence) [3] c) A radar is able to detect the reflected wave of an enemy s aeroplane after intervals of 0.2 milliseonds. If the velocity of the wave is 3 x 108 ms-1, calculate the distance of the aeroplane from the radar. [3] 0 ^_^0 ALL THE BEST 0 ^_^0 Std : 10 Subject : Physics Page : 5
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