1. Feb 9, 2015

### xxt

• Member warned: Non-Descriptive Thread Title
1. The problem statement, all variables and given/known data
A 2 kg sponge is dropped from rest, pulled down by gravity. how fast will it be travelling in 6 seconds, with a 5 N force of air resistance acting on it ?

2. Relevant equations
vf= vi+ gt (im just guessing coz im not sure )

3. The attempt at a solution
the speed in 6 seconds ?? (im not sure what to write here)

2. Feb 9, 2015

### Bystander

3. Feb 10, 2015

### ehild

Welcome to PF!

The wording of the problem is not clear, did you copied it correctly? Was it not "how fast will it be travelling in the 6th second" ?
Anyway, it is said that also air resistance acts on it, in addition to gravity. So what is the acceleration of the sponge? vf=vi+gt is valid when the only force is gravity.

4. Feb 10, 2015

### terryds

First, find the acceleration using the Second Newton Law
Then, use the formula vf= vi + at to get the final velocity (Note : Use negative sign for the opposite direction of the falling ball)