### Class XI

A coin kept on a rotating gramophone disc just begins to slip if its centre is at a distance of 8 cm from the centre of the disc. The angular velocity of the gramophone disc is then doubled. Through what distance, the coin should be shifted towards the centre, so that the coin will just slip?
1. 2 cm
2. 6 cm
3. 16 cm
4. 4 cm
A ball being kicked by a foot and rising at an angle of 30. o from the horizontal. The ball has an initial velocity of 5.0 m/s (Neglect friction). What is the magnitude of the horizontal component of the balls initial velocity?
1. 5.0 m/s
2. 2.5 m/s
3. 4.3 m/s
4. 8.7 m/s
A car of mass 800 kg moves on a circular track of radius 40 m. If the coefficient of friction is 0.5, then maximum velocity with which the car can move is
1. 8 m/s
2. 14 m/s
3. 12 m/s
4. 7 m/s
One radian is defined to be the angle subtended where the arc length S is exactly equal to the?
2. diameter of the circle.
3. circumference of the circle.
4. half of radius of the circle.
A body of mass 500 gram is rotating in a vertical circle of radius 1 m. What is the difference in its kinetic energies at the top and the bottom of the circle?
1. 4.9 J
2. 19.8 J
3. 2.8 J
4. 9.8 J
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