# Force Diagram

## Homework Statement

I have to draw a force diagram for a rock dropped off a cliff at the moment of release.
Is there any force acting upward on the rock at the moment of release?

none

## The Attempt at a Solution

I know the force of gravity acts downward on the rock. My thinking is that the only force acting on the rock at the moment of release is gravity downward, then as it falls there is air resistance upward and a greater force of gravity downward. When a rock hits it's terminal velocity however the forces of gravity and air resistance are equal. Is this correct?

## Answers and Replies

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tiny-tim
Science Advisor
Homework Helper
Hi cheerspens!
I know the force of gravity acts downward on the rock. My thinking is that the only force acting on the rock at the moment of release is gravity downward, then as it falls there is air resistance upward and a greater force of gravity downward. When a rock hits it's terminal velocity however the forces of gravity and air resistance are equal. Is this correct?
Equal and opposite!

Otherwise, completely correct!

(i assume you're supposed to ignore the atmospheric pressure all round the rock )