Question

A ball is projected from origin with a speed of 20m/s at an angle of 30

Answer 1

for the final velocity v to be perpendicular to the initial velocity it has to turn down 60 degree from the horizontal.

the horizontal component of "v" v Cos 60 remains the same as the horizontal component of initial velocity 20 cos 30.

Hance = 20 (cos 30) / (Cos 60) is equal to 20 10 60 = 30.64 m/s

vertical component of "v" - v sin 60 is equal to minus 30 m/s.
minus to denote downward direction .

change in velocity in the vertical direction is - 30 - 20 sin 30 = - 40 m/s.

Time = -40 / -g = 4 second.