1. Mechanical Equilibrium
Total forces = 0

2. N Suppose Tia weights 200 N How much is the tension on the string? 200
100
100

3. Equilibrium (Equal) N
If all the forces acting on an object are balanced (equal to zero), the object is in equilibrium.
There are two types of Equilibrium:
Static and Dynamic

4. Name the forces here N
Tension 1
Tension 2
Painter 1’s Weight
Scaffold’s Weight
Painter 2’s Weight
means
Painter 1’s weight + Scaffold’s weight + Painter 2’s weight - tension 1 - tension 2 = 0

5. For a scaffold in equilibrium
Tension N
Tension
Painter’s Weight
Scaffold’s Weight
Painter’s Weight
The sum of upward forces equals the sum of downward forces.
ΣF = 0 and the scaffold is in equilibrium

6. N
Try this one
Draw the force diagram first.
150 N

7. N
And another
Draw the force diagram first.
450 N

8. N What is the tension? Hint: The man is in the center
What is the weight of the man and the staging?
600
= 1200 N

9. If the painter moves to the right:
Would decrease
Would increase
400 N
How would the tension in the ropes change?
What is the total weight of painter and staging?
= 1200 N
What is the net force?
1200N – = 0
It is in static equilibrium
800 N

10. What is the tension in each string?
600
600
Total downward force = = 1200 N
Since man is in the middle, this force is divided equally on both strings.
1200 ÷ 2 = 600 N each

11. What is Nisha’s weight if
She stands on two bathroom scales and each scale reads 200 N?
200 N N = 400 N

12. N
Another one
Two vertical chains are used to hold up a 1000 N log. One chain has a tension of 400 N. What is the tension in the other chain?
Log Weight - Tension 1 – Tension 2 = 0
1000N – 400 N – X = 0
600 N = X

13. Last one
1000
500
500
500
1000
If the crate and block move at constant speed, the tension in the string _______. This is ________ equilibrium
500

14. Work silently on worksheet
Refer to today’s notes to complete this worksheet.
Copying this worksheet will give you an “A” on this sheet and an “F” on the test.
Next class we have a test on this chapter.