A ball thrown horizontally from a point 24 m above the ground, strikes the ground after traveling horizontally a distance of 18 m. With what speed was it thrown, assuming negligible air
Resistance?
A) 8.1 m/s
B) 6.1 m/s
C) 7.4 m/s
D) 8.9 m/s

Question

Quizplus · Accepted Answer

The speed can be found using the formula for horizontal distance in projectile motion: $d = v \times t$, where $d$ is the horizontal distance, $v$ is the horizontal velocity, and $t$ is the time of flight. To find $t$, we use the vertical motion equation under gravity: $h = \frac{1}{2}gt^2$, where $h$ is the height (24 m) and $g$ is the acceleration due to gravity (approximately $9.8 m/s^2$). Solving for $t$ gives $t = \sqrt{\frac{2h}{g}}$, and substituting $h = 24 m$ and $g = 9.8 m/s^2$ gives $t = 2.2 s$. Substituting $t = 2.2 s$ and $d = 18 m$ into $d = v \times t$ gives $v = \frac{d}{t} = \frac{18 m}{2.2 s} = 8.18 m/s$, which rounds to $8.1 m/s$.

A Ball Thrown Horizontally from a Point 24 M Above