Freethought & Rationalism Archive

tronvillain · 05-31-2002, 01:30 PM

Godless Dave:

Quote:

However none of us are really at rest because we're standing (sitting in my case) on the surface of the earth, which is turning. Am I right that we can't feel that acceleration because the force of gravity holding us to the ground is so much stronger?

Actually, the only acceleration in that situation is due to the force of gravity. It's just that gravity pulls, while we're used to having forced that act by pushing. For example: you're inside a circular room that begins spinning - your inertia want you to be flung off in a straight line perpendicular to the spin, but instead you hit a wall which the exerts an inwards force on you. To be somewhat analagous to gravity, you'd have to set up a hugely strong vaccum in the centre of the room to pull you inwards.

Undercurrent · 05-31-2002, 01:38 PM

Quote:

Originally posted by ilgwamh:
<strong>Isn't a change in direction acceleration? Couldn't the earth be said to be continually accelerating as it travels round and round the sun?</strong>

Exactly. Acceleration is defined as change in velocity with respect to time, and velocity is a vector quantity and a change in direction is a change in the vector quantity.

m.

beausoleil · 05-31-2002, 01:44 PM

Best not to get too wedded to inertial frames. Whether you see a coriolis force and a centrifugal force depends on your frame of reference. Trying to distinguish 'illusory' from 'real' forces is actually quite problematic.

Mendeh · 05-31-2002, 01:51 PM

Thanks, everyone. I can now go forward with my life once more, knowing how acceleration works.

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05-31-2002, 01:44 PM	#13
beausoleil Senior Member Join Date: May 2002 Location: US and UK Posts: 846	Best not to get too wedded to inertial frames. Whether you see a coriolis force and a centrifugal force depends on your frame of reference. Trying to distinguish 'illusory' from 'real' forces is actually quite problematic.

05-31-2002, 01:51 PM	#14
Mendeh Regular Member Join Date: Aug 2000 Location: London, England Posts: 302	Thanks, everyone. I can now go forward with my life once more, knowing how acceleration works.

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