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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?
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