A projectile is launched vertically at 100 m/s. If air resistance can be ignored, at what speed will it return to its initial level?

Speed with which it return to its initial level is 100 m/s

Explanation:

We have equation of motion v² = u² + 2as

Initial velocity, u = 100 m/s

Acceleration, a = - 9.81 m/s²

Final velocity, v = ?

Displacement, s = 0 m

Substituting

v² = u² + 2as

v² = 100² + 2 x - 9.81 x 0

v² = 100²

v = ±100 m/s

+100 m/s is initial velocity and - 100 m/s is final velocity.

Speed with which it return to its initial level is 100 m/s