Given that the mass of the rock is, m = 7.51 kg
The height of the bridge is, h = 4.5 m
The potential energy of the rock is
[tex]P\mathrm{}E\text{. =mgh}[/tex]Here, the acceleration due to gravity, g = 9.8 m/s^2
Substituting the values, the potential energy will be
[tex]\begin{gathered} P\mathrm{}E\mathrm{}=7.51\times9.8\times4.5 \\ =331.191\text{ J} \end{gathered}[/tex]The potential energy will be converted to kinetic energy
[tex]PE\text{ = K E}[/tex]Also, Kinetic energy will be
[tex]\begin{gathered} KE\text{ = }\frac{1}{2}mv^2 \\ v=\sqrt[]{\frac{2KE}{m}} \end{gathered}[/tex]Here, v is the speed of the rock.
Substituting the values, the speed of the rock will be
[tex]\begin{gathered} v=\sqrt[]{\frac{2\times331.191}{7.51}} \\ =\sqrt[]{88.2} \\ =9.391\text{ m/s} \end{gathered}[/tex]The speed of the rock will be 9.391 m/s
