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Khud Ko Badlo Tumhare Liye Swath Badal Jayagi

  • Date Submitted: 08/28/2011 06:56 AM
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Assignment III, 2011 Subject : Physics Date of Submission : 02.09.2011 1.

MPS : XI MM : 25

State whether the given statement is true or false and give reason. Work done in the motion of a body over a closed loop is zero for every force in nature . 1 A helicopter lifts a 72 kg astronaut 15 m vertically from the ocean by means of a cable. The acceleration of the astronaut is g/10. How much work is done by the following on the astronaut? a) The force from the helicopter. b) The gravitational force on him. Also calculate the Kinetic energy of astronaut. 3 a) A body is moving unidirectionally under the influence of a source of constant power. Show that its displacement in time ‘t’ is directly proportional to t3/2. Define coefficient of restitution.



b) 4.


Give reason. a) Sand is thrown on tracks covered with snow in hilly areas. b) It is difficult to start motion than to maintain it. c) A locomotive does no work against granty when it is running on a level plane with a speed of 60 km/h. 3 a) Rain is falling vertically with a speed of 30m/s. A woman rides a bicycle with a speed of 10m/s in the north to south direction. What is the direction in which she should hold her umbrella? A man can swim with a speed of 4Km/h in still water. How long does he take to cross a river 1 km wide if river flows steadily at 3 km/h and he makes his strokes normal to the river current? Also, find the distance covered by him down the river flow. 3 What is the difference in writing a length as 3.2cm and 3.200cm? Find the value of 60 W on a system having 100 g, 20 cm and 1 minute as the fundamental units. 3




a) b)


Draw v - t graph for uniformly accelerated motion in the following cases: a) u= +ve , a = + ve b) u= –ve , a = +ve c) u= +ve , a = –ve



Show that for a projectile fired at an angle of elevation q , there are two times for which the projectile travels the same vertical distance. Also, prove that the sum of the two...


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