![]() This point could be a physical object or it could be a point outside of the object. The more mass an object has, the more gravitational force is exerted.Ĭenter of Mass is a term used by scientists to describe that point in an object where the object’s mass or weight seems to be concentrated. All mass-from the smallest sub-atomic particle to the largest star in the universe-exerts some amount of gravitational force. Gravity is a term used by scientists to describe the force of gravitation given on an object or near the surface of a celestial body such as the Earth, the moon, or another terrestrial planet. Just imagine: science bringing families together, one discovery at a time! I love it! Let’s start with a quick vocabulary lesson. The results are hilarious and unforgettable! As an added bonus, these challenges often bring my students’ families together as the students go home and challenge their siblings and parents to do them as well. In the end, these physical experiments allow my students to grasp the basic concepts of gravity and center of mass in a far more compelling way than they’d ever learn from any textbook. Lift a chair? Raise your leg? Pick up a quarter? No problem! (Or so they think…) I challenge my students to perform a series of seemingly simple physical tests, described below. When I teach about gravity and center of mass, for example, I like to shake things up by turning our classroom into an impromptu biokinetics lab. One of my favorite tricks is to get my kids up on their feet, doing science instead of reading about it. ![]() ![]() When the rug is thrown spinning into the air, the dot orbits around the COM (unless it has been stuck at the COM location).In my 13 years of classroom teaching experience, I’ve learned a few tricks to keep my students from becoming overwhelmed-or bored-by their science textbooks. A large movable dot (made out of Velcro™ and fluorescent tape) can be stuck anywhere on the rug lamina. ![]() The U-shaped object's COM is in the center of the U, not within the object itself. map is somewhere in Kansas (very likely where Dorothy and Toto reside). The plumb bob is any suitable weight on a string with a loop at the other end for quick hanging and removal from the anchor rod. The various suspension "points" on the lamina are actually holes, any of which are slipped over the anchor rod of the suspension assembly. The suspension mechanism is nothing more than a simple assembly of standard lab clamps and rods attached to the lecture table. If reasonable care is exercised, the chalk lines intersect at a single point - the COM. This is repeated from one or two other suspension points. A chalk line is drawn along the vertical plumb line. The lamina is hung from any of its suspension points with the plumb bob hanging from the same. The center-of-mass of an irregular shaped lamina is found by supporting it from various points. glued onto a 1/2" plywood board, (3) a U-shaped object made out of 3/16" plywood, (4) an asymmetric polygon shaped polystyrene sheet, and (5) an irregular shaped piece of rug which can be safely thrown, spinning in the air, and caught. They are (1) an amoeba shaped piece of masonite pegboard, (2) a cut-out map of the U.S. We have several irregular lamina to suspend and/or throw in the air. When an irregular shape is thrown into the air, it is seen to rotate about its marked center of gravity or center of mass (COM). The center of gravity fixed in (or outside) the object always orients itself with minimum potential energy on a vertical line below the support point. ![]() Center of gravity - center of mass - equilibrium ![]()
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