1. Aim: How do we solve static equilibrium problems?

2. Ex
A jet plane speeds up on the runway. You take out your yo-yo and notice that when you suspend it, it makes a 22 degree angle with the vertical.
What is the acceleration of the plane?
If the mass of the yo-yo is kg, what is the tension in the string?
a=3.96 m/s^2 F=0.423 N

3. Static Equilibrium
An object is in static equilibrium when it is at rest. What will the net force acting on the object in the x direction have to be? What will the net force acting on the object in the y direction have to be?

4. Tips for Solving Problems involving Static Equilibrium
Draw freebody diagram showing all forces acting on object. Write equation for net force in the y direction. Write equation for net force in the x direction. Solve for unknowns.

5. Ex1-Picture Hanging
A picture weighing 100 N is supported by two wires with tensions T1 and T2. Find each tension.
T1 = 50 N and T2 = 85.0 N

7. Ex2-Stoplight
A traffic light is supported by two wires. Find the tension in each wire. The stoplight has a mass of 30 kg.

9. Ex3- Three wire
The tension in wire A is 70 N. Find the tension in wires B and C.
Find angle ϴ
C = 50 N , theta = 45 degrees, B = 49N

11. Ex4
Find the tension in each wire.

13. Ex 5
A traffic light weighing 122 N hangs from a cable tied to two other cables fastened to a support. The upper cables make angles of 37 degrees and 53 degrees with the horizontal. These upper cables are not as strong as the vertical cable, and will break if the tension in them exceeds 100 N. Does the traffic light remain in this situation, or will one of the cables break?
73.4N and 97.4 N

14. Ex 5 (cont)
If the angles of the cables can be adjusted, in what situation does T1 = T2?