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Newton’s Law of Gravitation
Newton’s Law of Gravitation
Newton concluded not only that Earth attracts both apples and the Moon but also that every body in the universe attracts every other body; this tendency of bodies to move toward each other is called gravitation.
Center of gravity / mass
Center of gravity / mass
Definition of center of gravity:
The point through which the resultant of the weight of all the particles of the body acts.
Definition of center of mass:
The point that as though (1) all of the system’s mass were concentrated there and (2) all external forces were applied there.
Two different experiments based on the Center of Gravity concept
Two different experiments based on the Center of Gravity concept
Experiment 1:
Experiment 1:
Balancing soda can on its edge
Balancing soda can on its edge
Materials:soda can, water/soda liquid
Method
1)Empty out the Can and make sure all of the soda is taken out.
2)Fill the measuring cup to About 100ml.
3)Pour into the Canand balance it by leaning it on the edge.
Image of experiment
Image of experiment
The black point= center of mass
HOW DOES IT WORK-Analysis
HOW DOES IT WORK-Analysis
•The system will be stable if the center of mass, the black point, is over its base of support. This means if the point is between the vertical lines, the can will balance on its edge.
•The soda can could be balanced with little amount of water or soda is that gravity pulls the liquid towards the bottom and the center of gravity of the can is lowered. Then, the can stabilizes.
•It all has to do with weight distribution. The can looks as though it'll fall over, as it's leaning to one side but it's only the bottom portion of the can that's full of water! The can is pivoting on the point that's touching the table and there's an equal amount of twisting it over and pulling it back. It only looks as though it'll fall as it overhangs more on the one side but there is very little weight in that part of the can as it's empty.
Experiment 2:
Experiment 2:
Balancing utensils on the rim of glass
Balancing utensils on the rim of glass
Materials: fork, spoon, toothpick, glass cup
Method
1)Startby pushing the two center tines on the fork upward a little.
2)Putthe fork and spoon together so that the the spoon can be under the two center tines, but over the outer two tines of the fork.
3)Balancethe utensils on a fingertip to find the middle point, where the toothpick should be inserted between the utensils. Work the toothpick into the tines of the fork.
4)Burnthe end of the toothpick hanging over the inside of the glass.
Image of experiment
Image of experiment
HOW DOES IT WORK-Analysis
HOW DOES IT WORK-Analysis
•The center of gravity of an object refers to the central location that gravity acts on the object. In this activity, the center of gravity is straight down from the spot where the toothpick sits on the rim of the glass (called the pivot point). If you look closely at your balancing utensils, you’ll notice that the handles are curved well below the toothpick. This actually moves the center of gravity directly below the point where the toothpick touches the rim.
•If the glass has slanted sides, the center of gravity— where the utensils balance front and back, left and right, up and down— is actually located in mid-air next to the glass. A tightrope or high wire walker often uses a long stick for balancing in the same way as the forks are used in this experiment.
•If you burned the ends of the toothpick, you may have been surprised that the utensils remained balanced. Why didn’t the flame keep burning and cause a collapse? Fire requires three things: heat, fuel, and oxygen. Take away one of these and the fire goes out. The fuel and oxygen were there but you took away the heat. The glass and the metal rob the flame of its heat and it dies.
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