you are standing at the top of a cliff that had a stairstep configuration. there

Question

you are standing at the top of a cliff that had a stairstep configuration. there is a verticle drop at 7 m at your feet, then a horizontal shelf of 7 m, then another drop of 3 m to the bottom of the canyon, which has a horizontal floor. you kick a 0.64 kg rock, giving it an initial horizontal velocity that barely clears the shelf below. what initial velcity will be required to barely clear the edge of the shelf below you? the acceleration of gravity is 9.8 m/second squared. consider air friction to be negligible. answer in m/s

Explanation / Answer

So, to solve this problem, you first need to understand the amount of time the rock has to clear the 7m horizontal shelf. That is the same as the amount of time to fall 7m down.

Since the object is initally at rest, y = (1/2)gt2. Solve for t:

t = (2y/g). we know that y = 7m, so

t=(14/9.8) = 1.20s

So, the rock must be moving horizontally at a speed fast enough to clear the 7m shelf in 1.20s.

V = x/t = 7m/1.20s = 5.83 m/s

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