# Homework Help: Newton's Law

1. Oct 15, 2014

### rlagustn

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An object with a mass if falling with a force that is equal to its own weight of 25 pounds. The air resistance causes a decelerate force equal to 1/2 the velocity of the object at any time. If the object falls from rest, what is the velocity of the object after 8 seconds?

I'm just confused at the wordings of the question. I just cannot find a way to start.
I tried to use to formula v(t) = (mg/b)t - (m^2*g / b^2) + m/b*vknot but the formula did not make sense to me. I was wondering if there are any other formulas I could use to solve this problem.

2. Oct 15, 2014

### Simon Bridge

Start with a free body diagram - draw all the forces on the object, the use Newton's laws.
You'll end up with a differential equation.

3. Oct 15, 2014

### nasu

It is confusing. "Falling with a force" does not make much sense.
And a force equal to 1/2 the velocity it's definitely nonsense. The units do not match.
Is this the actual text of the problem?