0MIAMI DADE COLLEGE/North Campus

PHY1004/PHY2053/PHY2048

Diego Cely

Garifullina Leysan

Monica Camargo

Tereza M Gago

April 19, 2013

4.9

1.96

1.921

0.196

0.196

196

((8.82-8.78)/8.789)*100 = 0.45

Fs1+Fs2+W = 1.96+4.9+1.921 = 8.78 N.m

Fs1+Fs2 = 3.92 + 4.9 = 8.82 N.m

500

0.5

4.9

3.92

0.4

400

3.414

2.45

0.768

0.196

0.500

0.400

F2

W

4.9

1.92

1.96

Fs2

Fs1

4.9

3.92

0.7

0

3.43

3.43

0

((3.414-3.43)/3.43)*100 = 0.47

2.058

1.568

2.058

0.588

4.9

1.47

0.3

0.3

1.96

Fs2

F1

0.49

0.1

4.9

0.4

3.92

F2

((2.058-2.058)/2.058)*100 = 0

Static equilibrium is:

A system of particles is in static equilibrium when all the particles of the system are at rest and the total force on each particle is permanently zero. This is a strict definition, and often the term "static equilibrium" is used in a more relaxed manner interchangeably with "mechanical equilibrium", as defined next. An object with forces acting on it, but that is not moving, is said to be in equilibrium.

Mechanical equilibrium for a particle is:

The necessary and sufficient conditions for a particle to be in mechanical equilibrium is that the net force acting upon the particle is zero

The necessary conditions for mechanical equilibrium for a system of particles are:

1. First Condition of Equilibrium

We may say that an object at rest is in equilibrium or in static equilibrium. Newtons First Law of Motion describes an object at rest. An object in static equilibrium has zero net force acting upon it. The First Condition of Equilibrium is that the vector sum of all the forces acting on a body vanishes. This can be written as F = F1+ F2+ F3+ F4+ . . . = 0

Where , the Greek letter sigma, again means the summation of whatever follows -- the summation of the forces, in this case. That's all there is!

However, remember the following:

Ensure that you have included all the forces. This means carefully draw a free body diagram. Include gravity (the weight) and all contact forces.

Remember that forces are vectors. That means that the first condition of equilibrium,

F = 0 - really means: Fx = 0,

Fy = 0

2. Second Condition of Equilibrium

An object in equilibrium does not move along a straight line -- it does not translate -- that means the sum of all the forces on it is zero. That was the first condition of equilibrium.

But an object in equilibrium also does not rotate. That means the sum of all the "rotational forces" or torques on it is also zero. The sum of all the torques on an object is equilibrium is zero. This is the Second Condition of Equilibrium.

Torques that would rotate an object counter clockwise may be taken as positive and torques that would rotate an object clockwise may be taken as negative. Then we can write this Second Condition of Equilibrium as

or we can calculate the sum of the clockwise torques and set them equal to the sum of the counterclockwise torques. Then we can write this Second Condition of Equilibrium as