Free fall on a small airless planet. A rock released from rest to fall on a small airless planet falls y = gt^2 m in t sec, g a constant. Suppose that the rock falls to the bottom of a crevasse 20m below and reaches the bottom in 4 sec. A) Find the value of g. B) Find the average velocity for the fall. C) With what velocity did the rock hit bottom?

If a rock released with an initial velocity = u

If it falls under gravity 'g' for 't' seconds,

Expression to find the distance covered will be,

If the initial velocity is zero expression for the distance covered will be,

Here, g = Gravitational pull Or acceleration due to gravity

A). If the distance covered 'y' = 20 m

     And t = 4 seconds

     By substituting these values in the expression,

      m per sec square

B). Average velocity of a free falling body =

    Initial velocity of the object = 0

    Final velocity =

                           =

                           = meter per sec.

    Therefore, average velocity =

                                                    = meter per second

C). Since, the rock hits the bottom after seconds,

     Velocity with which the rock will hit the ground

                                                                                      m per sec.

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