In projectile motion, the modulus of rate of change of velocity

A ball is rolled off the edge of a horizontal table at a speed of $4\, m/s$. It hits the ground  after $0.4\, sec$. Which statement given below is true?

A stone is tied to a string of length $L$ is whirled in a vertical circle with the other end of the string at the centre. At a certain instant of time, the stone is at its lowest position and has a speed $u.$ The magnitude of the change in its velocity as it reaches a position where the string is horizontal is

Average velocity of a particle is projectile motion between its starting point and the highest point of its trajectory is : (projection speed = $u$, angle of projection from horizontal= $\theta$)

The $x-t$ graph of a particle moving along a straight line is shown in figure The $a-t$ graph of the particle is correctly shown by

A body of mass $m$ is suspended from a string of length $l$. What is minimum horizontal velocity that should be given to the body in its lowest position so that it may complete one full revolution in the vertical plane with the point of suspension as the centre of the circle