# Homework Help: Another SUVAT problem

1. Dec 5, 2015

### Rumplestiltskin

1. The problem statement, all variables and given/known data
a) How much time does a dropped weight take to fall 120m down a cliff? (I answered this correctly as 4.9s -- √(s/0.5 x g).)
b) What would the time be (in question a) if the weight was thrown downwards at 2.5m/s?

2. Relevant equations
SUVAT

3. The attempt at a solution
None, apart from a mistaken rearrangement of s = ut + 0.5at^2.

2. Dec 5, 2015

### RUber

I am not familiar with SUVAT, could you provide more detail?
In your equation S = Ut+ .5At^2, the only thing that changes from your first problem is that now u is not 0.
You will end up with a quadratic equation for t. Pick the positive solution.

3. Dec 5, 2015

### Rumplestiltskin

How would I isolate t?

4. Dec 5, 2015

### SteamKing

Staff Emeritus
Have you ever solved a quadratic equation?

5. Dec 5, 2015

6. Dec 5, 2015

### Rumplestiltskin

My bad, I was trying to rearrange for t. This crossroad is new to me.

120 = 2.5t + 4.9t^2
4.9t^2 + 2.5t - 120 = 0

A quadratic formula later... 4.7s. Correct! Thanks all.