A ball is thrown 125 m upward and then falls the same distance back to the Earth. Neglecting air resistance, its total time in the air is about
A)5 s.
B)10 s.
C)15 s.
D)more than 20 s.

Question

Quizplus · Accepted Answer

The total time in the air can be calculated using the formula for the time of flight for a projectile launched vertically: $t = \frac{2v}{g}$, where $v$ is the initial velocity and $g$ is the acceleration due to gravity (approximately $9.8 \, \text{m/s}^2$). Since the ball travels 125 m upward and then the same distance downward, we can use the kinematic equation $v = \sqrt{2gh}$ to find the initial velocity for the upward journey, where $h$ is the height (125 m). Plugging in the values, we get $v = \sqrt{2 \times 9.8 \times 125}$. The exact numbers are not necessary to calculate because the question is conceptual and asks for an approximate time. Knowing that the time to rise and the time to fall are equal, and given the options, a total time of around 10 seconds is reasonable for such a motion, considering the acceleration due to gravity and the distances involved.

A Ball Is Thrown 125 M Upward and Then Falls