16.At the instantaneous centre, the velocity of the moving lamina at any instant is

17.The maximum value of the horizontal range for a projectile projected with a velocity of 98 m/sec is

18.A projectile has maximum range of 40 m on a horizontal plane. If angle of projection is a and the time of flight is 1 second, then sin a must be about

19.For a given velocity of a projectile, the range is maximum when the angle of projection is

20.A circular disc rotates at n rpm. The angular velocity of a circular ring of same mass and radius as the disc and to have the same angular momentum is