Neglecting air resistance, a ball projected straight upward so it remains in the air for 10 seconds needs an initial speed of
A)50 m/s.
B)60 m/s.
C)80 m/s.
D)100 m/s.
E)110 m/s.

Question

Quizplus · Accepted Answer

The time it takes for the ball to reach its peak is half of the total time in the air, so 5 seconds. Using the formula for the velocity of an object under gravity (v = gt, where g is the acceleration due to gravity, approximately 9.8 m/s^2), the initial speed needed is 9.8 m/s^2 * 5 s = 49 m/s, which is closest to 50 m/s.

Neglecting Air Resistance, a Ball Projected Straight Upward So It