[Math] When a rock hits the ground, the velocity is zero. But, what is acceleration

calculus

Disclaimer: I am not a student trying to get free internet homework help. I am an adult who is learning Calculus from a textbook. I am deeply grateful to the members of this community for their time.

When graphing acceleration or v'(t), should you put a "hole" in the endpoints of the graph?

Let's look at the typical graph of a rock being thrown, where s(t) = inverted parabola.

v(t) is a diagonal line going from positive to negative (eg: y=-32t+4)

a(t) = v'(t) = constant (negative) (eg: y=-32)

Let's say the rock hits the ground at t=10. What should acceleration be EXACTLY at t=10? Is it still -6, like the times before it? Or does it not exist since at t=10, the rock has stopped. Can you have acceleration when velocity = 0? I guess you can b/c acceleration at the peak position (vertex of parabola) is still negative -6, even though the rock is not moving in that peak's instant. Can you take the derivative of the point at t=10 on the velocity graph?

I saw the sample problem does NOT create a hole at the very end of the A(t) graph when the rock hits the ground. So, the graph is saying the Acc. is still the same as when it was falling a moment before. It also fills in the A(t) at t=0, even though the rock is not yet moving and has velocity = 0 at t=0

etc etc etc….

Best Answer

This is not a mathematics question, but a physics question. Mathematically, all I can tell you is that if $f$ is a quadratic function (an inverted parabola), then $f''$ is constant, therefore it takes the same value at $10$ as it does everywhere else.

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