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Topic Summary

Posted by: KentPDG
« on: 12 March, 2009, 12:10:32 AM »

Robin is about right.  More specifically, the resistance one feels when pushing or pulling an object equals the Weight times something called The Coefficient of Friction.  The Coefficient of Friction differs among materials; it is high for, say, unfinished wood and low for, say, polished marble.

When you push an object, typically you are pushing downward; i.e., your hands are below your shoulders.  Thus the pressure you apply is at a downward angle.  It can be depicted as two components: a forward force, and a straight-down force.  The straight-down component adds to the weight bearing down on the floor.  Hence, the total resistance is increased.

When you pull an object, typically you are pulling upward; i.r., your hands (once again) are below your shoulders.  Thus the pressure you apply is at an upward angle.

Aha, you are ahead of me.  Yes, the pulling force also divides into two components -- one parallel to the floor, and one straight up.  The latter is counter to the weight of the object, hence there is less load bearing down onto the floor.  The total resistance is therefore decreased; i.e., less frictional force when pulling, than when pushing.

In fact, if the object is light enough (say, a sack of potatoes) the upward component of your pull will be greater than the weight of the object and you will lift it off the floor.  Then, no resistance to motion (other than inertia).

This kind of stuff is taught in the first or second year of Engineering school, in courses designated Theoretical and Applied Mechanics, or T&AM -- known to generations of overstressed incipient engineers as Torture and Applied Misery.
Posted by: robinsamuels
« on: 11 March, 2009, 08:42:24 PM »

As you push, the far end is forced downwards, increasing resistance.

I find that it is much easier to push thing when sitting on the floor and pushing with my legs. That way, the force is going straight, not downwards.
Posted by: Hiheels
« on: 11 March, 2009, 08:41:52 PM »

This seems to be especially true on carpet...

I think it's because any play in the carpet is kept down by your feet so you don't end up trying to push it against a home made speed bump.
Posted by: redslap
« on: 11 March, 2009, 08:40:07 PM »

This seems to be especially true on carpet...