Is the acceleration due to gravity (9.8 m/s^2) always present?

Question

I understand that the force of gravity is always present, and that in free-fall, an object's acceleration would be 9.8 m/s^2. But what about an object that is on the surface (like us), are we still experiencing the acceleration due to gravity?

Answer 1

No we are not. Not relative to Earth's surface anyway.



But here note this. g units are m/sec^2 acceleration units right? Well they are also Newtons/kg = kg.m/sec^2//kg = m/sec^2 as a Newton ~ kg.m/sec^2 by definition.



What that means is when you are not in free fall, g makes more sense if you realize it is also g = 9.8 Newtons/kg. So in W = mg the units for weight (the force of gravity ) are kg.Newtons/kg ~ Newtons, which we all recognize as a force unit. g is really a gravity force field, not an acceleration.

Answer 2

You have to distinguish between the force of gravity which is your weight, and the acceleration due to gravity, which is 9.8 m/s², approximately. They are not the same.



Which the other answers don't realize.



You ask "is the acceleration due to gravity always present" ? and the answer to that is NO, you have to be falling to experience that acceleration. Acceleration is a change in velocity, so you have to have an increasing velocity to have an acceleration.



But you do experience the force of gravity, that is what keeps you on the surface of the earth, and the value of that force is your weight.



.

Answer 3

Like other people said, no. Acceleration is a change in velocity, and when you are sitting still, acceleration is zero.



However, one time I was working with accelerometers (solid state devices that measure acceleration in different directions) and I figured out pretty quickly that there was always a signal in the vertical direction. The vertical accelerometer always thought there was an acceleration of 9.8 m/sec^2 and you had to account for that in determining the actual acceleration.



What it really was doing was responding to the force of gravity compressing the device, not an actual acceleration. It was illustrating the equivalence of those two effects.

Answer 4

Drop the ball from varying heights and measure the time it takes to hit the ground. Graph the results. If you have access to a camera that can take a series of shots, take a set in front of a tape measure. If you can use a strobe light that flashes every 1/10 of a second or so, use that. Note that if you drop it from too high, or use too light a ball, air resistance will slow it down and you'll no longer be measuring the acceleration due to gravity. I won't describe it fully. You need to think about that.

Answer 5

Yes, you are. The only reason that your velocity, and you, don't "accelerate" is that you have nowhere to go.



The following equation can be used to describe velocity in this case:



Vf = SQRT { Vi^2 + [2ad] }



Vf = Final velocity

Vi = Initial velocity

a = Acceleration (in this case, gravity)

d = Displacement



So... You're just standing there, which means that your initial velocity (Vi) is 0.0 m/s. There is nowhere for you to move (displace) so that is also 0.0 m.



Put those into the equation above, and even though a = 9.81 m/s^2, your final velocity = 0.0 m/s



Your force is normal force, and Earth is exerting an equal force against you. But these forces would not exist without constant gravitational acceleration.

Answer 6

no .. we are experiencing a force but that force is cancelled by the normal force

thus, the net force on a normal person standing on a surface is 0 .. so there is no acceleration involved



one can only experience an acceleration when his/her velocity is changing but since we're not going up or down .. the net acceleration on us (in the vertical axis) is 0.

Answer 7

yes, the force of gravity is always working on every physical object on the Earth. That is why our weight is measured in Newtons (N) which is mass x acceleration due to gravity. The reason to why we do not accelerate downwards because of this acceleration is because of course the normal force of the ground counters the force of our weight due to gravitational acceleration.

Answer 8

Ya no matter where you go as long as your on earth the acceleration due ot gravity is the same. If you went to another planet it would be different but on earth even if we're standing on the ground gravity is still pulling us down at a rate of 9.8 m/s/s which keeps us ffrom floating away.