Static Equilibrium

Static Equilibrium1. Identify the object of interest.

2. Draw a free-body diagram.

3. Choose a coordinate system.

4. Write out Newton's 2nd law for each component of the coordinate system.

5. Choose a pivot point.

6. Write out the torque equation using for clockwise torque and + for counter-clockwise torque.

7. Solve system of equations for unknown values.

Grocery Sign• A grocery store sign has a

mass of 50 kg and is centered on a 8 kg rod which is 2.0 m long. What is the tension in the support wire, and the force exerted by the wall on the rod?

JordansGrocery

30°

Up the Ladder• A 4.0 m long ladder is placed

against a very slick wall at an angle of 60° with respect to the floor. The coefficient of friction between the ladder and the floor is 0.40. How far up the ladder can a 60 kg person go before the ladder begins to slip?

Race Down the Slope

• A block and a ball move down an inclined plane. The block is able to slide while the ball has enough friction to roll.

What are the velocities when they reach thebottom of a 0.25m highslope assuming frictionalloses are negligible?

At the Arcade• An 8.0 kg bowling ball is rolled from x=6m

to the left. What velocity is required to get it to x=1m?

-60 -40 -20

0 20 40 60 80

100

0 1 2 3 4 5 6

Position (m)

Height vs Position

Pot

enti

al E

ner

gy (

J)How high is the hump?

Where will the ballend up in the future?

Where are the turningpoints if the ball is atx=1m with 20 J of energy?

Stability• Determine stability through the potential

energy function.

Unstable StableNeutral

dU

dx0

d U

dx

2

20

d U

dx

2

20

d U

dx

2

20

• Equilibrium

604020

0-20-40

100

-60

80

3210 4 5 6

Height vs. Position

Pot

enti

al E

ner

gy (

J)

Position (m)

Classify Stability• How would your classify the following?

(Stable, Unstable, Metastable, Neutral)

A

B

C

D

EF

GH