Question

question 6 of 10
a boy throws a football horizontally from a window that is 2.8 m above the ground. if he throws the ball with a speed of 12 m/s, how far from the window does the ball land?
a. 9.1 m
b. 4.3 m
c. 11.2 m
d. 0.23 m

Explanation:

Step1: Calculate time of fall

Use vertical - motion equation $h = v_{0y}t+\frac{1}{2}gt^{2}$. Since the ball is thrown horizontally, $v_{0y} = 0$. So $h=\frac{1}{2}gt^{2}$, and $t=\sqrt{\frac{2h}{g}}$. Given $h = 2.8$ m and $g = 9.8$ m/s², $t=\sqrt{\frac{2\times2.8}{9.8}}\approx\sqrt{\frac{5.6}{9.8}}\approx\sqrt{0.5714}\approx0.756$ s.

Step2: Calculate horizontal distance

Use horizontal - motion equation $x = v_{0x}t$. Given $v_{0x}=12$ m/s and $t = 0.756$ s, $x=12\times0.756 = 9.072\approx9.1$ m.

Answer:

A. 9.1 m