A stone falls from rest from the top of a cliff, a second stone is thrown do wnward from the same height 2sec later with an initial speed of 30m/s. If both stones hit the ground below simultaneously, how high is the cliff?

The cliff is 12.632 meter high.

Explanation:

Each stone experiments a free fall motion, that is, an uniformly accelerated motion due to gravity. We construct the respective equations of motion for each stone:

First stone

(1)

Second stone

(2)

Where:

, - Final height of the first and second stone, in meters.

, - Initial height of the first and second stone, in meters.

, - Initial speed of the first and second stone, in meters per second.

- Time, in seconds.

- Gravitational acceleration, in meters per square second.

If we know that , , , and , then we find that time when both stones hit the ground simultaneously is:

The height of the cliff is:

The cliff is 12.632 meter high.

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explanation:

measuring things 1 litre of water