# Freefall distance problems solver

This calculator solves problems on passed distance during freefall

Here is the typical freefall distance problem: A free-falling body without initial velocity passed 2/3 of its path at the last second of its fall. Find the entire distance traveled by the body.

The same task can be formulated more simply: A free-falling body with initial velocity v0 passed K part of its distance for the last n seconds. Find the entire distance the body traveled.

It's possible to create a calculator for such problems. Below you will find the calculator that solves the task for given v0, n, K, and g (free-fall speed). And the process of solving is written in formulas below the calculator.

#### Free fall. Distance passed task.

Digits after the decimal point: 2
Fall time

Distance passed

### Solution

To begin with, we write the known conditions as formulas:
The total distance the body passed
$S=V_0t+\frac{gt^2}{2}$

Distance passed without the last n seconds of the fall
$S'=V_0(t-n)+\frac{g{(t-n)}^2}{2}$

It is known that the difference between the two is a certain amount of K of the total distance
$V_0t+\frac{gt^2}{2}-V_0(t-n)-\frac{g{(t-n)}^2}{2}=K(V_0t+\frac{gt^2}{2})$

Next, expand the brackets, translate everything left, reduce and sort the monomials by degree t. As a result, we obtain the following
$-\frac{Kg}{2}t^2+(gn-KV_0)t-\frac{gn^2}{2}+V_0n=0$

We get the conventional quadratic equation with respect to t with the following coefficients
$a=-\frac{Kg}{2}$
$b=gn-KV_0$
$c=-\frac{gn^2}{2}+V_0n$

All the figures for the calculation of the coefficients are known from the condition. And I hope everybody can solve quadratic equations.

We have to choose the correct root only. It's obvious that if there are no roots, there is no solution. If there are, then the desired root must be greater than n (otherwise, it makes no sense), and if both of the roots more than n, the smaller one will suit us.

When we find the time, the distance passed can be found by substituting the first formula.

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PLANETCALC, Freefall distance problems solver