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STD.IX PHYSICS. DON BOSCO ACADEMY, PATNA FIRST TERM EXAMINATION 2020-21 DATE:08.09.2020 F.M.50 TIME:1HR.30 MIN. Multiple Choice Type: Choose the correct option and write the option with the relevant wordings or numerals given alongside your selected option. (1x10=10 marks) Question-1. a). 1 A is equal to i) 0.1nm ii) 10 10 cm iii) 10 8 m iv) 10 4 b). A seconds pendulum is taken to a place where acceleration due to gravity decreases to one fourth its original value. The time period under the changed condition will be i) unchanged ii) doubled iii) th the original value iv) four times . c). When glass objects fall on the floor they break, while when they fall on foam they do not because (i) time taken to come to rest on foam is short and force is great (ii) time taken to come to rest on the ground is more so force is greater (iii) time taken to come to rest on the foam is more so the Force is less (iv) none of these A train moving with a velocity of 20ms 1 is brought to rest by applying brakes in 5 sec. The retardation will be i) 4 ms 2 ii) 100 ms 2 iii) 5 ms 2 iv) 25 ms 2 A force is needed to i) change the state of rest ii) change the state of uniform motion iii) change the direction of motion iv) all of the above f. The relation between rate of change of momentum and magnitude of force is i) F= d). e). ii) F= (mv mu)t g). h). i). j). iii) =mv mu iv) F(mv mu) =t Newton s third explains i) inertia ii) magnitude of the force iii) direction of the force iv) the interaction of the forces between two bodies. The force of attraction between two bodies at a certain separation is 10N. If the separation is reduced to half the force of attraction will (i) decrease (ii) no change (iii) increase (iv) incomplete data The pressure P1 at a certain depth in sea water and P 2 in river water at the same depth are related as i) P 1=P2 ii) P1 P2 iii) P2 P1 iv) P1 P2 = 0 When the barometer level falls gradually, it indicates about the weather i) stormy weather ii) rainy weather iii) dry weather iv) extremely dry weather. Question-2. Solve the following numerical showing the necessary steps. a). b). c). d). (3X10=30) A seconds pendulum is taken to a place where acceleration due to gravity increases four times. What will be the effect on the time period of the pendulum ? A car travels the first 20 km of a journey at a uniform speed of 40 kmhr 1 and the next 20 km at 50 kmhr 1.Calculate the average speed of the car? A body initially at rest travels a distance of 200m in 10 s with a constant acceleration .What will be the final velocity at the end of 10s. A train starts from rest from Patna Jn and accelerates uniformly at a rate of 1 ms 2 for 100 sec and then maintains this speed for 50 sec and brakes are applied and the train is brought to rest in the next 20 sec .Calculate the maximum speed attained by the train? -2e). A ball of mass 100g is moving with a velocity of 50ms 1 . On applying a force with a bat for 1 sec the ball acquires a velocity of 60 ms 1 .Calculate the magnitude of the force applied by the bat. f). Two balls A and B are of masses m and 2m are in motion with a velocity of v and 2v . Compare (ratio) the forces that will be to bring them to rest within the same time . A body is thrown vertically upwards with an initial velocity u . Calculate the maximum height S attained by the body where acceleration due to gravity is g . required g. h. i. j. The force of attraction between two bodies at a certain separation is 100 N. What will be the force of attraction between them , when the distance between them is doubled . A cube of side 10 cm is immersed in a liquid. The liquid pressure on the upper face of the cube is 10 Pa. Ignoring atmospheric pressure ,calculate the thrust on this face. The atmospheric pressure at a place is 75 cm of Hg. What will be corresponding pressure in Pa. Show working. Question-3. The diagram given below represents a circular path motion of a body. Complete the following statement with appropriate words in the blank spaces given: The motion is uniform_____________ and variable _______ [2] Question-4. The diagram below shows a horizontal spring with two objects A and B attached to its ends with the spring COMPRESSED. What do the forces F F represent (2M) Question-5. The diagram below shows a horizontal spring with two objects A and B attached to its ends with the spring STRETCHED. What do forces represent [2 M] -3Question-6. What does the below given graph represent about atmospheric pressure and altitude. Name an instrument that is based on information derived from this graph. Question-7. The diagram below is an inflated balloon with its opening fitted into a hollow straw mounted on a pencil top. What will you observe when the air is released ? Which law is being illustrated ? (2M) ******************* (2M)
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