How come "terminal velocity" and "final velocity" are different?

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Terminal velocity is defined as the maximum speed an object reaches when the force of air resistance equals the force of gravity, resulting in zero net force. The final velocity of a bullet can be less than terminal velocity if it does not have enough time to reach that speed before hitting the ground. The equations provided illustrate the relationship between initial velocity, terminal velocity, and the effects of air resistance on the bullet's motion. Understanding this distinction is crucial in physics, as it highlights how external forces influence an object's speed. Ultimately, the final velocity can be lower than terminal velocity due to the time constraints of the bullet's flight.
Ted goldmund lee
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Homework Statement



Someone shot the bullet perpendicular to the ground. And there is air resistance.
Velocity of bullet is
v^2 = Ae^(-2kx)-g/k upward
v^2 = g/k-Be^(2kx) downward

A,B is constant, g is a gravitational acceleration, k = c2/m , c2 is a resistance constant, m is a mass of bullet.

When air resistance is C2v^2 show that final speed of the bullet is

VoVt/Root(Vo^2+Vt^2) , Vo is initial velocity and Vt is terminal velocity.

Homework Equations



I thought that terminal velocity is the velocity when there is no net force on the object.
Since there is no parasutre, shouldn't the final velocity is same with terminal velocity?
How come final velocity is smaller than terminal velocity...
( I am pretty sure in this question we don't have to consider air density )

The Attempt at a Solution



upload_2019-2-27_23-46-25.png

I did solve this mathmetically but I just don't understand the physical concept.
How can something be slower when net force on it is zero.
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Ted goldmund lee said:
Since there is no parasutre, shouldn't the final velocity is same with terminal velocity?
Terminal velocity is the fastest it can go due to air resistance. Final velocity may be less if it hits the ground before making it all the way up to terminal velocity.
 
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The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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