Looking at the calculus in a catapult

In the graph below, there are two equations. The position being represented by the black line, and the velocity being represented by the blue line. When a person catapults a ball into the air, its position changes over time (or x). At different positions, the ball has different velocities. This is represented by the velocity. It measures its rate of change over time as well.

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position
velocity

By moving point A or a, you can see the position at that value of x.

Picture Sources:
grass = http://openclipart.org/detail/171366/grass-only-by-cyberscooty-171366

App generated by Geometry Expressions