Training Lesson

1. Balancing act on see-
saw
Objectives
 Students investigate the center of mass
(gravity) of an object by experiment.
 Students explain the reason why see-saw
is balanced (or clockwise torque is equal to
the counter-clockwise torque) by
experiment.

2. Balancing act on see-saw
Demonstrate to find the center
of mass of 1-m ruler.

3.  Center of mass
Balancing act on see-
saw
Center of mass there is place
where net torque acting on the
body is zero.
Center of mass (gravity) is the
point where all of the mass of the
object is concentrated.
Center of mass (gravity) is a place
where it divides masses into two
parts equally.
Why do you think so???

4. Balance of see-saw
Balancing act on see-
saw
See-saw makes balance then the mass
from each side time its distance from
pivot equals each other.
See-saw makes balance then the
masses at the both side of pivot
equal each other.
See-saw makes balance then the
clockwise toque equals to the
counter-clockwise toque.
Why do you think so???

5. Procedures
Balancing act on see-
saw
Find the enter of mass
Find the balance of see-saw
Mark

6. Results
Balancing act on see-
saw
Get g = 10 N/kg
Length
d1= (cm)
d = (cm), d2 = d/2 = (cm)
Weight
m1 = (g)
m2 = (g)
Torque 1 = 2
(m1 d1 g = m2 d2 g)
m1 d1 = (g cm) = (kg m)
m2 d2 = (g cm) = (kg m)
1 = 2 = (Nm)

7. Simple calculation
Balancing act on see-
saw
show your work
•m1 d1 =
•m2 d2 =
•1 = m1 d1 g =
•2 = m2 d2 g =

8. Conclusions
Balancing act on see-
saw
• Center of mass (gravity) is the point where all of the
mass of the object is concentrated or is place where
net torque acting on the object (body) is zero.
•The see-saw makes balance then the clockwise toque
equals to the counter clockwise toque. These can be
found easily by experiment.

9. Do it more!
• For the uniform rod or ruler
•For uniform ring and hollow cylinder
C

10. Thank you so much!