If an object is say thrown down (vertically) at an initial speed that is faster than its terminal velocity, what would happen to that objects speed? Would it slow down?
Newtonian Mechanics – What Happens if Starting Speed Exceeds Terminal Velocity?
dragnewtonian-gravitynewtonian-mechanicsprojectilevelocity
Best Answer
Yes. The object will slow down to its terminal velocity if its speed starts higher than its terminal speed.
The net force on a falling object of mass $m$ near the surface of the earth is \begin{align} F = F_\mathrm{drag} - mg \end{align} where $F_\mathrm{drag}$ is the force due to air resistance, I have assigned "up" to be the positive direction, and $g$ is the magnitude of the acceleration due to gravity near the Earth's surface. When the drag force is greater than $mg$, the net force will be positive, and by Newton's Second Law, the object's acceleration will point upward and will slow the object down. This will reduce the drag force until the drag force and weight are equal, the object's acceleration is zero, and the object will have constant speed -- it's terminal speed.