Apr 30 2008
Learning Physics At The Grocery Store Check Out Counter
Everything I wanted to know about Physics I learned at the Grocery Store check out counter. How so you ask? Well simple and let me explain. You have a Can of Arizona Ice Tea and 3 cans of Raviolis. Can you stack them on top of each other so they do not fall when the checker steps on the conveyor belt peddle? Yes or No?
Ah ha, you see how important simple life observations can be to learning physics? Now then on the grocery story “product-alator” or conveyor belt challenge; are you up for it? Have you ever thought about this or stacked things to see if they would stay when the belt moves? Most of us have, perhaps giving in very little thought.
Yes I have done this too. I stack bottles of sodas or cans in lines paralleling the direction of travel. As the conveyor moves it moves all the cans or bottles against each other. None fall down because they are affected at slightly different intervals or because they block each other. You know like the silver spherical balls hanging and you hit one and the one on the end move but none other. Yet if you start with two, then the two on the end move
instead.
This is why Row houses in Earthquakes all fall down if the Earthquake goes one way and none fall down if it goes the other way? Depends if you house is facing North or South or if it faces East or West. So if you put Your Ice Tea in the back with two cans in front in a row upright and the third can of ravioli onto of the second can they will stand upright and not fall. How do I know? I have envisioned this and done it.
This is because Ice tea Can is taller. It will prevent the reactionary acceleration of the can on top from falling off. The can in front will push against the second can, lodged in place by the heavier second can, with weight on top and the ice tea in back.
If the whole system rocks forward the Ice Tea will not move due to the weight to knock off the top can of ravioli and the Top can of ravioli can still slide forward a little bit, as the reaction force will be less than the original force. I have noticed that the second forces are lessoned with each rocking.
For instance the Car Dummies in crash testing, they hit something, slam against the dash board and then slam back against the seat and then the dashboard for a second time. Each time less force. Also remember liquid moves too and density matters and the liquid will wish to move at a different rate than the cans, they are part of system within a system which is actually not entirely the same system.
This indeed makes this technique work even better from my own personal experience of stacking at the grocery store. I stack two liter bottles of Soda against each other in a row any other way they all fall down. I absolutely find the this topic of interest because I too have observed this and am always thinking of this stuff when loading the conveyor.
In fact I had a comment or two yesterday when a lady said I have been doing groceries for 25-years, but my husband thinks I am stupid and he always loads the cart onto the conveyor.
It was a funny conversation and I said well with all the heavy industry this state is known for that makes sense from a Finite Capacity Scheduling Model. Limited goods, limited space, each product needs to be put in a certain bag. Cold with cold; Chips not with cans, etc. We all had a laugh. But of course I always observe everything like you. Everyone should learn about physics by observing. Consider all this in 2006.
Lance Winslow
Tags: Grocery Store Check Out Counter, Learning Physics