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Re: [Phys-l] definition of gravity



Are you saying that if one experiences an acceleration due to some unknown interaction we must call it "gravity?"

What if, in reality, the acceleration is due to and EM interaction (but that fact is still unknown)? That is, there is an electric field which interacts with the residual charge on my body and causes an upward force resulting in a net acceleration equal to the centripetal acceleration needed to keep me stationary with the Earth but slightly out of contact with the floor. Is the gravitational acceleration field near zero in my reference frame? I know that the gravitational pull of the Earth has not quit. If I don't know what it is that's making this happen, do I say that gravity has quit or do I look for a force from another source and say that the gravitational field is still close to 9.8 N/kg?

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
bounces@carnot.physics.buffalo.edu] On Behalf Of John Mallinckrodt
Sent: Tuesday, November 08, 2011 9:37 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] definition of gravity

You are in a rocket whose motors are producing precisely enough thrust
to cause it to accelerate at 9.8 m/s^2. You are standing on a scale on
the floor that reads the same weight that it does when used on the
surface of the Earth.

Question 1: Does anyone have any qualms whatsoever about calling what
you are experiencing a gravitational force that is every bit as "real"
as any gravitational force can possibly be?

Question 2: Does anyone have any qualms whatsoever about saying that
you find there to be a gravitational field of 9.8 N/kg directed toward
the floor of the rocket?

John Mallinckrodt
Cal Poly Pomona
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