# A marble dropped from a bridge strikes the water in 5.0 s. what is the height of the bridge? (Answer in meters)A

Jun 6, 2018

$\text{122.5 m}$

#### Explanation:

Use equation of motion

${\text{S" = "ut" + 1/2"at}}^{2}$

Where

• $\text{S =}$ Displacement covered
• $\text{u =}$ Initial velocity
• $\text{a =}$ Acceleration (It’s ${\text{9.8 m/s}}^{2}$ due to Earths gravity)
• $\text{t =}$ Time taken to cover displacement $\text{S}$

Marble is dropped. It means initial velocity ($\text{u}$) of marble is $0$

Therefore the equation becomes

${\text{S" = 1/2"at}}^{2}$

color(white)("S") = 1/2 × "9.8 m/s"^2 × "(5 s)"^2

color(white)("S") = 122.5\ "m"

Displacement covered by the marble when thrown from the bridge is obviously height of the bridge.