To solve static problems: 1. Make a free-body diagram showing all forces on each object. 2. Choose a coordinate system and resolve forces into components. 3. Write equilibrium equations for the sum of forces in each direction and the sum of torques. 4. Solve the equations to determine the unknown forces.

1. Section 9.2
Solving Static Problems

2. Solving Static Problems
• How do I solve static problems?

3. Solving Statics Problems
1. Choose one object at a time, and make a free-body
diagram showing all the forces on it and where they
act.
2. Choose a coordinate system and resolve forces into
components.
3. Write equilibrium equations for the forces.
4. Choose any axis perpendicular to the plane of the
forces and write the torque equilibrium equation. A
clever choice here can simplify the problem
enormously.
5. Solve.

4. See Saw
A board of mass M = 2.0 kg serves as a see
saw for two children. Find x.

5. Balancing Forces
A uniform 1500 kg
beam, 20.0 m
long, supports a 15,000
kg printing press 5.0 m
from the right support
column. Calculate the
force on each of the
vertical support
columns.

6. Homework
• Page 247, # 1 - 8

7. Cantilevers
• A beam that extends
beyond its supports
• Diving board
• If you get a – sign on
your force, it means it
points in the opposite
direction

8. Cantilevers
• How would you set up
the torque and force
equations?

9. Homework
• Page 247, # 9 - 15

10. Example
• If there is a cable or
cord, it can only
support forces along
its length.
• Forces perpendicular
to a cable would
cause it to bend

11. Example
A uniform beam, 2.20 m
long with a mass of 25.0
kg, is mounted by a
hinge on a wall. The
beam is held by a cable
with an angle of 30°
from the beam. The
mass of the sign is 28.0
kg. Find the FT in the
cable and the x and y
components of FH.

12. Homework
Page 248, # 18 – 24, skip 21