STATIC EQUILIBRIUM AND ROTATIONAL QUANTITIES

1. STATIC EQUILIBRIUM

2. STATIC EQUILIBRIUM
Static equilibrium occurs when an
object is not moving and not rotating.
Static means not removing
Equilibrium means balance

3. STATIC EQUILIBRIUM
Examples:
A seesaw balanced with equal weights
A hanging picture that does not tilt
A bridge that stays steady

4. Conditions for
Static Equilibrium

5. Conditions for Static
Equilibrium
For an object to be in static equilibrium,
two conditions must be satisfied:
1. Forces must balance
 Total upward forces = downward forces

6. Conditions for Static
Equilibrium
1. Forces must balance
Examples:
A ruler balanced on a pencil (pivot) does
not move up or down when foces are
equal

7. Conditions for Static
Equilibrium
2. Torques must balance
-Total clockwise torque = total
counterclockwise torque
-Torque = turning effect of a force

8. Conditions for Static
Equilibrium
2. Torques must balance
Formula:
Torque = Force x Distance from pivot

9. Conditions for Static
Equilibrium
3. Understanding Torque
Torque is the “twisting” effect that
makes an object rotate.

10. Conditions for Static
Equilibrium
3. Understanding Torque
Factors that affect torque:
a. Force - The heavier the weight, the
bigger the torque

11. Conditions for Static
Equilibrium
3. Understanding Torque
Factors that affect torque:
b. Distance from pivot – The farther the
force is from the pivot, the bigger the
torque

12. Conditions for Static
Equilibrium
3. Understanding Torque
Examples:
Pushes near the hinge – hard to open
= small torque
Push at the hande – easy to open =
large torque

13. 4. Visual Examples
A. Balanced Seesaw
-Forces are equal
-Torque are equal – Seesaw stays level

14. 4. Visual Examples
B. Unbalanced Seesaw
Left torque > Right torque – Left goes
down

15. Conditions for Static
Equilibrium
5. Vectors in Static Equilibrium
Vectors are arrows that shows direction
and magnitude of forces

16. Conditions for Static
Equilibrium
5. Vectors in Static Equilibrium
Examples:
Downward = weight (force due to and
magnitude of forces
Upward arrow = support force (pivot or
table)

17. Conditions for Static
Equilibrium
5. Vectors in Static Equilibrium
-When vectors cancel each other -
object is balanced

18. Conditions for Static
Equilibrium
6. Real – Life Applications
-Bridges and buildings ( forces and
torques balanced)
-Seesaws and playground equipment
-Balancing scales in the laboratory

19. Conditions for Static
Equilibrium
6. Real – Life
- Tightrope walking (pole balances
torques)

20. Questions:
1. What does static equilibrium
mean?

21. Questions:
2. What are the two conditions for
an object to be in static
equilibrium?

22. Questions:
3. How can a lighter person
balance a heavier person on a
seesaw?

23. Questions:
4. Give an example of static
equilibrium from your home or
school.

24. Questions:
5. What is torque, in simple terms?