If an object is dropped from a helicopter, when it reaches terminal velocity what happens?

Question

A. the acceleration finally reaches g.
B. the total force is zero
C. gravity no longer acts upon it
D. all of the upward forces add up to zero
E. the accerleration of gravity becomes 0

Answer 1

B. is almost correct the sum of all forces (in the up/down direction) is zero. I say "almost" because there could very well be imbalanced sideways forces (like winds) even though terminal velocity has been reached.

A. is incorrect because at terminal velocity a = 0; this results because f = 0 = ma; the net vertical forces (f) are zero

C. is incorrect because all mass has weight, no matter what other forces are acting on it. As W = mg; there is always g the acceleration due to gravity.

D. is incorrect because the drag friction force D > 0. It has to be because f = W - D = 0 at terminal velocity (a = 0), which means D = W > 0 so that D > 0

E. is incorrect because g is a constant greater than zero, no matter what's going on with the mass m of your object

Answer 2

B. the total force is zero

Terminal velocity is reached when the force of air resistance would equal the weight of the object. The resultant force is zero at equilibrium. Force is equal to acceleration times a constant, which is the mass (F=ma). There fore, acceleration cannot be g but zero, which means A is not true. Gravity still acts on it because it still pulls the object down, but at a constant velocity, which means C is not true as well. There is an upward force, which is the air resistance, so D is not true. Acceleration of gravity remains as a non zero constant, it just so happens that it is no longer part of the equation, so E is wrong.

Answer 3

Fuzzy terminology leads to debatable answers!

In my opinion, the correct answer is E.
"Acceleration OF gravity"?
Gravity doesn't accelerate -- OBJECTS being acted upon BY gravity accelerate!

E. Since the object is moving at a constant speed in a consistent direction there is no longer any acceleration.
We are talking about the object's acceleration here, not "g."
This one is also debatable since the phrase does not specify whether we are talking about "the OBJECT'S acceleration" or "the acceleration DUE TO gravity" (which is the constant "g.")

It is not A because acceleration is not a limit that can be "finally reached." Acceleration is a CHANGE RATE.

It is not B because we are talking about:
NET force = 0, not
TOTAL force = 0.
This one is debatable depending on your definition of "TOTAL."

It is not C because gravity IS acting upon it. The force of gravity is just being offset by the force of resistance.

It is not D because if all of the upward forces added up to zero there would be no resistance and the object would still be accelerating.
.

Answer 4

At terminal velocity the upward force of air resistance upon a body exactly balances the downward force from acceleration by gravity. Cf: Stokes Law.

Answer 5

B
If an object attains a terminal velocity, that means it no longer is accelerating and since F=ma, total force=0. The weight is balanced by the air resistance.

Answer 6

The force of friction exactly matches that of acceleration. The net effect is that the falling object is kept at a constant speed, of course if the air is thickening the friction will increase and the velocity will lower, however for the question you asked the answer is B.

Answer 7

at the same time as the item reaches terminal velocity, the acceleration via gravity = the air resistance. so the item does no longer boost up anymore because it falls . it falls at a consistent velocity.

Answer 8

B
the force due to gravity = the force due to air resistance
air res increases as v does.

Answer 9

Yea..yea ..I got it,it is B,...but what is the helicopter for?