Answer
See answer.
Work Step by Step
Equation 2-11c relates the vertical displacement to the initial vertical velocity, the final vertical velocity, and the acceleration.
The balls have the same vertical displacement, the same final vertical velocity of zero, and the same acceleration. This means that their initial vertical velocities are the same.
If 2 objects are tossed upward with the same initial vertical velocities, they will spend exactly the same time in the air.
Imagine the situation: the ball thrown at the shallower angle has a larger initial speed, because 2 two balls have the same initial vertical velocity. This ball reaches the maximum height at the same time as the other ball, thrown at the steeper angle.
