Question

The magnitude of the initial velocity of the particle

Answer 1

By question it is given that velocity at the top most point is half the magnitude of the initial velocity.Therefore the vertical velocity at the highest point is zero and their remains only the horizontal velocity i.e and it is final velocity at the topmost point.And by question we know that final velocity is half of magnitude of the initial velocity

Answer 2

Answer:

Zero if it is starting from rest.