Drag Force

1. Jul 11, 2009

clarineterr

1. The problem statement, all variables and given/known data
A baseball is thrown straight up. The drag force is proportional to v^{2}.
In terms of g, what is the y-component of the ball's acceleration when its speed is half its terminal speed and it is moving up? In terms of g, what is the y-component of the ball's acceleration when its speed is half its terminal speed and it is moving back down?

2. Relevant equations

v terminal = $$\sqrt{mg/D}$$

3. The attempt at a solution
I honestly have no idea how to attempt this problem

2. Jul 11, 2009

RoyalCat

The drag force is of the form:
$$F_d = -kv^2$$

$$F_d = -Dv^2$$

The terminal velocity is achieved when the ball starts falling at a constant velocity. At that point, the following holds true:
$$kv^2=mg$$

3. Jul 11, 2009

tiny-tim

Hi clarineterr!

Start "acceleration = dv/dt = … "