what is the weight of a body falling uniformly towards earth surface?

Question

i came across a word problem in which the weight of a body was asked. The body was supposed to attain terminal velocity means falling uniformly.

If the answer is zero then what is the weight of free falling body.

Answer 1

Weight of a body is defined as the force with which the earth attracts the body towards its center. Close to the surcafe of the earth, all bodies are attracted by the force, mg, where m = mass of the body and g = 9.8 m/s^2 which is acceleration due to gravity. A body falling with a terminal velocity near the surface of the earth DOES NOT have its weight zero, but it is also mg. Almost zero gravity can be experienced only at great distances from the surface of the earth wher the value of g is very small, where the force of attraction by the earth will be very small and hence the weight will also be very small. Astronauts experience this condition of near weightlessness.



EDIT: If by weight one means what a spring balance will record, it is zero, but that is not the real weight. By definition, real weight is the force with which the body is attracted by the earth. If an object immersed in a liquid is weighed, it will weigh less, but that is its apparent weight and not real weight.

To understand the difference between the real weight and apparent weight, please refer to the following link and read it fully.



EDIT:



When terminal velocity of the body becomes constant, no net force acts on it. Though there are forces acting on the body, the resultant of all these forces is zero. Three forces are considered to be acting on the body:

( 1 ) its, weight, mg, downwards

( 2 ) Force of buoyancy, Fb, upwards and

( 3 ) Force of air resistance, Fr, upwards

As these forces balance,

mg - Fb - Fr = 0

=> real weight, mg = Fb + Fr and it is not zero.

mg - Fb - Fr is called the apparent weight which is zero.

Answer 2

When a body reaches terminal velocity v ~ constant, the net weight w = W - D ~ 0 is almost zero. But the actual weight W = mg remains the same when g ~ constant near Earth's surface.



The air drag D ~ rho V^2 depends on the shape and aerodynamics of the falling body, plus the air mass density rho and the velocity V of the fall relative to the air. Thus, as the body picks up velocity V and gets closer to Earth where rho is larger, the drag D gets larger and offsets more of the weight W. Finally W <= D and the net weight w ~ 0 so the body no longer accelerates to a greater V.



In fact, the body will actually decelerate a bit due to the increasing rho as the body approaches the ground. So there really isn't a terminal velocity where there is absolutely no change in velocity, but the change is very small during the latter part of the fall. For all intents and purposes the velocity is constant when W = D so that w = 0.

Answer 3

Weight of free falling body is zero. Weight of body attained terminal velocity is zero too.

Answer 4

Weight of a body at terminal velocity is equal to the force of the air resistance ====> weight is balanced by air resistance ===> which by Newton's First Law is equal to your weight standing on the earth





In free fall, the weight = 0 because the above ai resistance force is not present.

Answer 5

Newton taught us that an object's motion is not necessarily in the same direction as the exerted force. Instead, it's more correct to say that the "change in motion" is in the direction of the force. In a nutshell: if the object is moving opposite the force, the force will slow it down; if it's moving toward the force, the force will speed it up. And if it's moving at right-angles to the force, the force will curve its path. In all these cases, the "change" is toward the force, even though the actual direction of motion may not be. You see this when you throw a baseball. Gravity creates a combination of slowing down, speeding up, and a curving path. Of course, the baseball's path soon intersects with the ground. But if you could throw a baseball fast enough--about 5 miles per second (and could somehow avoid the air resistance), the ball would cover a great distance before gravity had time to curve the ball's path much. In 1 second, this super-ball would travel 5 miles horizontally while gravity would make it dip down only 16 feet vertically. But here's the thing: Because the world is round, the earth's surface itself dips down 16 feet in 5 miles. So that means the ground would drop 16 feet just as the baseball drops 16 feet. As a result, the baseball would be just as high above the ground as when you first threw it. And it would still be travelling horizontally at 5 miles/sec, so it would repeat this feat, second after second, without ever getting closer to the ground. In effect, the ball is "dropping" due to gravity, but the ground is "moving out of the way" as the ball drops. The net result is that it just keeps going, until it has circled the earth. And why stop there? It circles the earth again and again. It's in orbit. Near the earth's surface, 5 miles/sec is the "critical speed" to keep from dropping closer to the ground, and that's about the speed at which "low" satellites travel (like the ISS, which is about 230 miles up). You can do the same thing at higher altitudes, but there the critical speed is smaller, because the gravity is weaker. At the distance of the moon, the "critical speed" is about 2/3 miles per second (about 2000 mph). If you go SLOWER than the critical speed, you'll start to bend down closer to the earth, and indeed will speed up, just like a falling baseball does. But that doesn't necessarily mean you'll hit the earth. If you're sufficiently high up, and your horizontal speed is sufficiently fast, you'll curl AROUND, approaching the earth but not hitting it, until you are on the earth's opposite side, again traveling horizontally, but at a faster speed and a lower altitude than before. At that point, you're now going FASTER than the critical speed, so your path will widen as it curves, once again opening up distance between you and the ground. You continue to gain altitude (and slow down) as you curve around the earth, until finally you reach your initial (slow, high) position. Then the cycle repeats. So it is with the planets around the sun. They're each going pretty close to the "critical speed" for their own distance from the sun. But not exactly. During each orbit, sometimes they are a little closer (and faster), and other times they are a little farther (and slower).

Answer 6

Weight is a function of mass (which whatever you do remains constant), and the acceleration due to gravity, which is dependent on your location. Assuming that wherever you are on earth, the acceleration due to gravity is constant, that is 9.8m/s^2, then your weight will still be the same as it is when you are not falling.

Answer 7

its not an answer , but can you please specify the velocity?it seems like the question is not bad