Do now: Where would you place your
finger on a ruler if you wanted to ruler
to balance on your finger?
Balancing Act
Center of Mass - the point where an
object is perfectly balanced!
The center of mass is a position defined relative to an object or
system of objects. It is the average position of all the parts of the
system, weighted according to their masses.
Demonstrations of center of mass
ACTIVITY TIME!
Bring a small object and line up against the wall outside of the
classroom. BE VERY QUIET PLEASE!
What’s so important about the center
of mass (C.o.M.)?
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Real objects are more complex than a single particle
Can treat entire object as if its entire mass were contained at a
single point, known as the object’s center of mass
Center of mass is the weighted average of the location of
mass in an object.
Sample Problem
Find the center of mass of the object shown below.
CENTER OF
MASS
Center of Mass of uniform objects
If an object is made up of one type of material (same density
throughout) and is symmetric like a ruler, textbook, and wood
plank. The C.o.M. is located at the geometric center of the object!
For a multi-mass system
Find the center of mass of an object modeled as two separate
masses on the x-axis. The first mass is at 2 kg at an x-coordinate
of 2 m and the second mass is 6 kg at an x-coordinate of 8 m
Calculating C.o.M. for Particles
x : position
m: mass
cm : center of mass
Solution
This means that this system is
equivalent to having a 8 kg at the 6.5 m
location!
In this balancing act activity,
we want the center of mass
to be at the 0 meter mark.
The seesaw is unbalanced
because currently the center
of mass (CoM) is not at the 0
meter mark.
Our goal is to figure out
where we should place the
other mass to make the COM
at 0 meters
https://www.youtube.com/watch?v=tk_ZlWJ3qJI&t=557s
If you understand the physics behind
each game and apply the concepts…
HOMEWORK
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COMPLETE ALL 3 LEVELS OF THE BALANCING ACT!
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Take a selfie with the screen once complete and submit on Google Classroom.
MUST EARN AT LEAST 20/24 stars!
Check if collisions are elastic, inelastic, perfectly inelastic, or explosions from the two
momentum worksheets!