CIRCULAR MOTION 08 MOTION Class 9th Science (Physics) (Practice Sheet) 1 Which of the following is an example of circular motion? A. A car moving on a straight road. B. A pendulum swinging back and forth. C. Earth revolving around the Sun. D. A ball thrown vertically upwards. 2 In circular motion, the direction of the velocity vector is: A. Inward towards the center. B. Outward away from the center. C. Tangential to the circle. D. Random and unpredictable. 3 The force that keeps an object moving in a circular path is called: A. Frictional force. B. Tension force. C. Centripetal force. D. Centrifugal force. 4 Which of the following is true for an object moving in uniform circular motion? A. Speed is constant, but velocity changes. B. Speed changes, but velocity is constant. C. Both speed and velocity are constant. D. Both speed and velocity change. 5 If the radius of a circular path is doubled while the speed remains constant, the centripetal force required will: A. Double. B. Halve. C. Remain the same. D. Become four times. 6 A wheel is rotating about its axis at a rate of 1200 rotations per minute. It comes to rest in 2 minutes. Determine the angular acceleration of a wheel. 7 Two bodies with masses m1 and m2 travel in a circle with radii r1 and r2 respectively. If they complete rotation in equal time, find the ratio of their angular speeds. 8 A ball of mass 0.5kg is attached to a string moving in a horizontal circle. If the tension in the string exceeds 25 N, the string will break. Find the maximum angular velocity of a ball with which it can rotate. The length of a string is 1.96m. 9 A biker is riding at a speed of 27km/h. As a bike approaches a circular turn on the road of radius 80m, the biker applies brakes and reduces the speed at the rate of 0.50m/s every second. Find the magnitude and direction of the net acceleration of the biker on the circular turn. 10 A man standing on an L.P. of a disc rotating on a table at the rate of 33 · 1 2 rpm. The distance of a man from the centre of the disc is 20cm. Prove that the friction coefficient between the man and the disc is greater than π 2 81 . (Take g = 10m/s2 ). Page 1 Email: Phone No: Website:
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