# Point-like body

Gold Member
my question is as follows:
when do we need to consider a three dimension body as a point like body in our calclulations?
i mean outside our theoretical/homework practices when should we assume the body as a point like?

one thing i can think of is when the geometric properties of a body is not important and therefore isnt taken into consideration into our calculations.
and maybe also when the body is a particle but other than that i dont know.

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When it makes it easier or possible to solve the problem.

pervect
Staff Emeritus
loop quantum gravity said:
my question is as follows:
when do we need to consider a three dimension body as a point like body in our calclulations?
i mean outside our theoretical/homework practices when should we assume the body as a point like?

one thing i can think of is when the geometric properties of a body is not important and therefore isnt taken into consideration into our calculations.
and maybe also when the body is a particle but other than that i dont know.
We can treat the Newtonian gravitational field (GM/r^2) of a spherically symmetric body as if the body were a point.

The center of mass is a useful concept for the motion of rigid bodies as well. If we apply a force to a rigid body, we know that the acceleration of the center of mass is F/m.

Danger
Gold Member
I don't do much in the way of science other than haunting these premises. My experience with your question actually is the basis of how I play and teach pool. When calculating how to hit a ball, I treat each one as a mathematical point rather than a spherical object. I then envision what angle to fire a laser at in order to achieve the proper 'reflection', followed by extrapolating the radii in order to accommodate the edge-to-edge contact of the balls.

Gold Member
Danger said:
I don't do much in the way of science other than haunting these premises. My experience with your question actually is the basis of how I play and teach pool. When calculating how to hit a ball, I treat each one as a mathematical point rather than a spherical object. I then envision what angle to fire a laser at in order to achieve the proper 'reflection', followed by extrapolating the radii in order to accommodate the edge-to-edge contact of the balls.
and ofcourse you always lose... :rofl:

Danger
Gold Member
loop quantum gravity said:
and ofcourse you always lose... :rofl:
Oooh... you sting me! (Wanna play for \$? :tongue: )