contestada

Figure 1.18 (Chapter 1) shows the Hoover Dam Bridge over
the Colorado River at a height of 271 m. If a heavy object is
dropped from the bridge, how much time passes before the
object makes a splash?

Respuesta :

Answer: 7.436 s

Explanation:

This situation is related to vertical motion, specifically free fall and can be modelled by the following equation:

[tex]y=y_{o}+V_{o} t+\frac{gt^{2}}{2}[/tex]  

Where:

[tex]y= 0m[/tex] is the final height of the object (when it makes splash)

[tex]y_{o}=271 m[/tex]  is the initial height of the object

[tex]V_{o}=0 m/s[/tex]  is the initial velocity of the object (it was dropped)

[tex]g=-9.8m/s^{2}[/tex]  is the acceleration due gravity (directed downwards)

[tex]t[/tex] is the time since the objecct is dropped until it makes splash

[tex]0=y_{o}+0+\frac{gt^{2}}{2}[/tex]  

Clearing [tex]t[/tex]:

[tex]t=\sqrt{\frac{-2y_{o}}{g}}[/tex]  

[tex]t=\sqrt{\frac{-2(271 m)}{-9.8m/s^{2}}}[/tex]  

Finally:

[tex]t=7.436 s[/tex]