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Introduction
How does the object balance? What is required to balance an object and how is this demonstrated?
Materials
hammer
ruler
string
long neck bottle
wooden board 1" x 4" x 18"
board with a 9" nail vertically standing from it
10 nails 9"
soda can empty
water
Small flat wooden board, 20” × 10”
PASCO Stability model
Procedures
The Balancing Coke Can the more famous between the experiments. Take an empty soda can and fill it up a third of the way. Tilt it at a 45 degree angle, be careful it will take a few times to get it. When the can is full the center of mass is in the middle and when titled the center of mass is above nothing that can withstand it. But with a third filled and at a 45 degree angle the center of mass is directly above the corner on which the can stands on.
The Hammer and the Ruler. Tie the string in a loop, put the hammer and the ruler through the loop. Slide the ruler on a table only 2-3 inches and have the hammer underneath the table, still through the string, the heavy part directly underneath the table.
The Pasco Stability Model. Place the stability model vertically on the table with the longer base touching the table. The hanging arrow indicates the center of mass of the model and where it aligns vertically with its base. Flipping the board over onto the shorter end the arrow points outside of the block of wood meaning that is where the center of mass is. The board topples over because nothing is holding up the center of Mass. Put the stability model on an incline and see where the arrow points. Now flip it over so the shorter end is on the incline. This will take a few tries to try and get it to balance, but watch where the arrow is pointing. Now the arrow is pointing at the very edge of the board. That is the new Center of Mass.
Balancing Nails. Take the board with the nail driven through it, place it flat on the table. Place one nail on the table lay 8 nails on top of the first nail heads touching the first nail in alternating pattern.lay the lat nail on top of the alternating nails with the head opposite of the first. squeeze the first and last nail together and place it on top of the vertical nail in the board.
Scientific Principle
These demonstrations are put together to show the Center of Mass or the balancing point of an object or system. There are two conditions that must be in place for an object to be balanced: transitional equilibrium and rotational equilibrium. Transitional equilibrium is when the net force on an object is zero. Rotational equilibrium is when net torque, on an object, equals zero.
Equation for force, as always, is
F= ma,
where F is force and its unit is N.
m is mass and its unit is kg.
a is acceleration m/s2
The equation for torque is
τ = F x d
where τ is torque and its unit is Nm
F is force and its unit is N.
d is the distance of the lever arm and its unit is meters.
Safety and Maintenance
All balancing objects may fall. Use caution to ensure that none of the objects you are balancing are in danger of breaking or causing injury if they fall.
If you choose to use any tools to help construct a demonstration system, please use extreme caution and observe all safety recommendations from the tool’s manufacturer.
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