<p> 4X2 Quiz on Circular Motion and Gravitation / Question paper: p.1 4X2 DSE PHYSICS Quiz on Circular Motion and Gravitation</p><p>Time Allowed: 30 mins. Class: 4 ____ Name: ______( )</p><p>Total Marks: 25 All answers should be done on the answer sheet provided.</p><p>Gravitational potential For uniformly v = u + at Equation Given: EP = mgh energy: accelerated motion : s = ut + ½at2 2 2 2 v = u + 2as Kinetic energy: EK = ½mv Newton’s law of Gm1m2 v2 gravitation: F = centripetal acceleration: a =  2r r 2 r</p><p>Take: acceleration due to gravity g = 9.81 m s-2 (close to Earth) universal gravitational constant G = 6.67  10-11 N m2 kg-2</p><p>Section A: Multiple Choices (Total 12 marks, 1.5 marks each)</p><p>1. A car moves through a circular arc of length l and radius r with a constant speed in time t. What is its angular velocity?</p><p> l l l 2πl A. B. C. D. 2πrt πrt rt rt</p><p>2. A coin of mass m is placed on a freely-rotating turn-table at a distance r from the centre. The mg maximum frictional force between the coin and the table is . The table's angular velocity is 2 steadily increased. The coin will begin to slide when the table's angular velocity is</p><p> g mg g gr A. B. C. D. 2r 2r 2r 2</p><p>3. The diagram represents the rear view of a motor car moving, away from an observer on a level road at a constant speed around a bend of which the centre of curvature is at P. Which of P the arrows best represents the direction of the resultant of the forces exerted by the road on the car?</p><p>A. B. C. D.</p><p>4. A particle is moving on a horizontal circular path with a constant angular velocity. Which of the following quantities of the particle remain constant?</p><p>(1) linear speed (2) kinetic energy (3) linear momentum</p><p>A. (1) only B. (1) and (2) only C. (2) and (3) only D. (1), (2) and (3)</p><p>5. The value g varies slightly with positions on the Earth’s surface. Which of the following statements are correct explanations? 4X2 Quiz on Circular Motion and Gravitation / Question paper: p.2</p><p>(1) The Earth is not a perfect sphere. (2) The Earth is not uniform in density. (3) The value G varies with positions.</p><p>A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3)</p><p>6. The moon orbits the earth once every 27.3 days, with a mean orbital radius of R. What is the period of an earth satellite with an orbital radius of R/30?</p><p>A. 4 hr B. 22 hr C. 68 hr D. 260 days</p><p>7. An astronaut in an orbiting satellite is sometimes said to be ‘weightless’. This condition occurs when (1) the gravitational attraction between the astronaut and the earth is just sufficient to provide the centripetal force which keeps him in orbit. (2) there is no reaction of the floor of the satellite on the astronaut’s feet. (3) the gravitational pull of the earth is exactly cancelled by the gravitational pull of the moon. A. (1) only B. (1) and (2) only C. (2) and (3) only D. (1), (2) and (3)</p><p>8. Which of the following statements concerning the observed acceleration due to gravity, g, at the surface of the Earth is/are true ? (1) The earth is not a perfect sphere so that g is greater at the poles than at the equator. (2) If the radius of the Earth decreases with its mass remaining unchanged, g at the poles increases. (3) If the speed of rotation of the earth increases, g at equator will be decreased. A. (1) only B. (1) and (2) only C. (2) and (3) only D. (1), (2) and (3) 4X2 Quiz on Circular Motion and Gravitation / Question paper: p.3 Section B: Structural Questions: (Total 13 marks) Write down all the answers on the spaces provided in the answer sheet.</p><p>1. A marble of negligible radius and mass 0.005 kg rolls in a horizontal circle of radius r = 8 cm inside inside a smooth semi-spherical bowl (fig.1.1). The radius R of the bowl is 10 cm.</p><p>R= 10 cm</p><p>A r= 8 cm a) Draw and label all thefig. forces 1.1 acting on the marble on fig.1.2. (2 marks) R= 10 cm b) Find the normal reaction acting on the marble at A. (3 marks)</p><p> c) Hence, find the speed of the marble. (2 marks)</p><p>2. The Hubble Space Telescope has a mass of 11 110 kg. It orbits around the Earth at an altitude of 559 km. Given: Mass of the Earth = 5.97 × 1024 kg Radius of the Earth = 6370 km</p><p>(a) What is the gravitational field at a point on the telescope’s orbit? (2 marks)</p><p>(b) What is the centripetal force provided to the telescope? (1 mark)</p><p>(c) What is the orbital speed of the telescope? (2 marks)</p><p>(d) What is the orbital period of the telescope? (1 mark)</p><p>End of Question Paper 4X1 Quiz on Circular motion & Gravitation/ Answer sheet: p.4</p><p>Answer Sheet for 4X2 Quiz on CM & g-field Class: 4 ____ Name: ______( ) Section A: Multiple Choices (Total 12 marks, 1.5 marks each) 1. 2. 3. 4. 5. 6. 7. 8. Section B: Structural Questions: (Total 13 marks) 1. (a)</p><p>(2 marks) (b) </p><p>(3 marks) (c) </p><p>(2 marks) 2. (a) </p><p>(2 marks) (b) </p><p>(1 mark) (c) </p><p>(2 marks)</p><p>(d) </p><p>(1 mark)</p><p>End of Answer Sheet</p>