Introduction to Classical Mechanics · Problem 3.16
Using F = ma — Morin
Physics — Mechanics · projectile_motion
Problem
Perpendicular velocities **
In the maximum-distance case in part (b) of the example in Section 3.4, show that the initial and final velocities are perpendicular to each other.
Hint: You can grind through this problem and explicitly find the final angle, but there's a quicker way. This quicker method makes use of the conservation-of-energy statement that the difference in the squares of the initial and final speeds depends only on the change in height (the relation happens to be vi2−vf2=2gh, but you don't need this actual expression). Consider the reverse path.