# Homework Help: Given 2 Sets of Data, Find 3rd (Velocity, Acceleration?)

1. Aug 17, 2010

### hatesmath

1. The problem statement, all variables and given/known data
Falling 20 yards above the ground takes 6 seconds to reach the ground.

Falling 100 yards above the ground takes 9 seconds to reach the ground.

How long would it take to reach the ground from 70 yards?

2. Relevant equations
v=d/t ?

I'm completely clueless. Any help with this would be greatly appreciated! Thank you.

2. Aug 17, 2010

### N-Gin

It's best to assume that body is accelerating at $a$ with initial speed $v_{0}$ and height $h_{0}$. Maybe some assumptions aren't true, but we don't know that before we try to solve the problem.

So, what you actually have is two equations of the form

$$h=h_{0}-v_{0}t-\frac{1}{2}at^{2}.$$

You are given the initial height and the time after which body falls on the ground (to the height $h=0$). That's all information you need.