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.

Balancing act on see-saw

 Demonstrate to find the center

of mass of 1-m ruler.

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???

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???

Procedures

Balancing act on see-saw

Find the enter of mass

Find the balance of see-sawMark

Results

Balancing act on see-saw

Get g = 10 N/kg

Lengthd1= (cm)

d = (cm), d2 = d/2 = (cm)

Weightm1 = (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)

Simple calculation

Balancing act on see-saw

show your work

•m1 d1 = •m2 d2 =

•1 = m1 d1 g =

•2 = m2 d2 g =

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.

Do it more!• For the uniform rod or ruler

•For uniform ring and hollow cylinder

C

Thank you so much!