A body is projected with an initial speed of 100√3 ms-1 at an angle of 600 above the horizontal. If g = 10ms-2 then velocity of the projectilea) Is perpendicular to its acceleration at the instant t = 15 sec.b) Is perpendicular to initial velocity of projection at t = 20 sec.c) Is minimum at the highest pointd) Changes both in magnitude and direction, during its flight.Mark the answer as

Time of flight , Acceleration of the projectile is vertically downward.At the highest point on its trajectory , velocity of the projectile is horizontal.The body arrives at the highest point on its trajectory at t = T/2 = 15 secHorizontal component of velocity remains unchanged and vertical component becomes zero at the highest point.Therefore magnitude of velocity becomes minimum at the highest point.Velocity becomes perpendicualr to the initial velocity at Therefore , option -(1) is correct.