Question

A stone is dropped from a bridge and reaches the bottom in 4 seconds.what is the height of the bridge?

Answer 1

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Answer on Question #41912, Physics, Mechanics | Kinematics | Dynamics

Question:

A stone is dropped from a bridge and reaches the bottom in 4 seconds. What is the height of the bridge?

Answer:

Height for uniformly accelerated motion equals:

$$h = H - \frac {g t ^ {2}}{2}$$

where $H$ is height of the bridge, $g$ is gravitational acceleration, $t$ - time.

The stone reaches the bottom then $h = 0$

$$H = \frac {g t ^ {2}}{2} = 9.81 * \frac {4 ^ {2}}{2} = 78.48 \, m$$

Answer: 78.48 m