Weight difference - pushing on Flat vs Grade
by Heishman on 07/31/03 at 09:38:55

I work at the Pierce County Jail in Tacoma Wa.  For safety reasons we are trying to determine the difference in weight of one of our food carts when pushed up a ramp vs. a flat surface.  The Cart weighs 440 lbs. fully loaded.  The cart dimensions are 30” x 40” x 6’.  The cart has 4, 6" wheels.  The ramp has a 1:12 grade.  We would like to know the approximate weight being pushed up the ramp.  Thank you.

Re: Weight difference - pushing on Flat vs Grade
by Robert Fogt on 07/31/03 at 13:47:05

The weight of the cart does not change, the amount of force required to push a cart up a hill is greater than on a flat surface.

There is a website here:
[url]http://www.school-for-champions.com/science/machines.htm[/url]

Scroll down to the part on ramps.

I also know that the amount of force required to move an object with wheels is:
(rolling resistance) * (weight of object) = (Force required to move it)

Automobile tires have a rolling resistance of 0.006 which is probably a bit less than your cart wheels.  If your cart had the same rolling resistance, it would take
0.006 * 440 = 2.64 pounds of force to push the cart on a flat surface.

I know that didn't directly answer your question. Perhaps there is a physics major reading who could explain it better.

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