Motion Under Gravity: Constant Velocity Explained

In summary, the two parachut divers jump from a plane and reach terminal velocity, but their speed is not constant because there is air resistance.
  • #1
Gughanath
118
0
I read a question about motion under gravity. It says that two parachut divers jump of a plane, and after a few seconds, they reach terminal velocity. Now, how is possible to have a constant velocity, if someone is falling under gravity (accelerating constantly)? :confused:
 
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  • #2
Because gravity is not the only force acting on the divers! The parachute allows the air to exert an upward force. When the divers reach terminal speed, the force of gravity (down) is exactly balanced by the air resistance (up). Thus: no net force, no acceleration.
 
  • #3
The air acts as a retarding force. This force is dependent on velocity. At some point, the velocity will be so great that the force due to the air friction, or drag, will be equal and opposite to gravity. From then on the forces are balanced and they have reached terminal velocity. Darn Doc Al, you beat me to it by a split second :tongue2:
 
  • #4
It's not possible; it is the increasing air resistance which eventually balances the force of gravity so that no NET force acts on the parachuter.

So, it is definitely NOT a free-fall situation.
EDIT:
I'm getting old and feeble..not one preposter, but TWO!
 
  • #5
So, first the divers falls under greavity, but eventually, the air resistance balances out the force of gravity, there the divers falls with constant velocity, since there is not net force acting?
 
  • #6
Gughanath said:
So, first the divers falls under greavity, but eventually, the air resistance balances out the force of gravity, there the divers falls with constant velocity, since there is not net force acting?
Correct.

Now what would happen if you jumped out of a balloon at 100,000 feet where the atmosphere is so thin it may as well not be there (this has been done)?
 
  • #7
From a Skydiver

Gughanath

Another part of your question is – Are you weightless?
A good way to demonstrate both of these yourself is come on out to a SkyDive Center and make a few jumps. If you use large plastic pop bottle vented but not so air will flow through it, and rig a spring stretched out by a weight when held vertical inside it.
It can be a bit tricky holding it vertical while exiting against the plane’s prop wash but the spring will pull the weight all the way up the moment you exit the plane.
That’s because you’ve started your Freefall –

Gravity will get you going til you reach terminal velocity in about 10 to 15 seconds. In prone postion that is about 120 miles/hr when your weigth is balanced out by the air cushion or “Drag” . And you can show that you really do have weight at this speed by checking out the weight protected from the wind in your bottle, It has by now completely stretched out the spring again. And you can boost that speed by manuvering to a head down or feet down position! With the lower Drag you can get up to at least 180 Miles/hr but after the 5 seconds or so it takes to get there – the spring will again feel a full stretch by the weight.
Althogh you may think you ‘feel’ weigthless while in Freefall – this will prove you are not.
(This also makes a great bar-bet as many a skydiver thinks they were wiegthless).

Note: Don't forget your chut as your TERMINAL VELOCITY >> your TERMINAL IMPACT SPEED --- unlike ant's and most small insects where there
TERMINAL VELOCITY >> insect TERMINAL IMPACT SPEED - lucky little guys get all the fun.

OK not up for going out of an Airplane – do a search on Indoor Skydiving.

Also – I have a First Cover on Joe Kittinger as first to Solo balloon accoss the Atlantic, and his info says he was also first man to go supersonic in a freefall by jumping from 102,800 feet.

RandallB
 

What is motion under gravity?

Motion under gravity refers to the movement of an object as a result of the Earth's gravitational pull. This type of motion assumes that there are no other forces acting on the object besides gravity.

What is constant velocity in motion under gravity?

Constant velocity in motion under gravity means that the object is moving at a constant speed in a straight line. This type of motion occurs when the only force acting on the object is gravity and there is no air resistance.

How is constant velocity in motion under gravity calculated?

Constant velocity in motion under gravity can be calculated using the equation v = gt, where v is the velocity, g is the acceleration due to gravity (9.8 m/s^2) and t is the time in seconds. This equation assumes that the object is moving in a straight line and there are no other forces acting on it.

What are some real-life examples of motion under gravity with constant velocity?

Some real-life examples of motion under gravity with constant velocity include a ball falling from a height, an object thrown upwards and then falling back to the ground, or a person jumping off a diving board into a pool.

Why is it important to understand motion under gravity with constant velocity?

Understanding motion under gravity with constant velocity is important for many scientific fields, such as physics and engineering, as it helps explain the movement of objects in the real world. It also allows us to make predictions and calculations about the behavior of objects under the influence of gravity.

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