Statics

Question 1

What is a vector?

Answer 1

A magnitude and a direction

Question 2

How do you add vectors?

Answer 2

Add i’s j’s and k’s.

Question 3

What is the difference between vectors and scalars?

Answer 3

Scalars only have magnitude, vectors have magnitude and direction.

Question 4

What does static equilibrium mean?

Answer 4

There’s no net force or torque.

Question 5

What are the sign conventions for tension and compression?

Answer 5

Tension is positive or away from the body. Compression is negative or towards the body.

Question 6

What does a pulley do to the tension in a cable?

Answer 6

It keeps it the same.

Question 7

Do you assume tension or compression for unknown variables?

Answer 7

Tension, and if you’re wrong, it’ll just be negative so you know it’s compression.

Question 8

Explain concurrent forces.

Answer 8

All lines of action interact at the same point. There are no moments.

Question 9

How do you find the equivalent point load magnitude of a distributed force?

Answer 9

Find the area of the shape.

Question 10

How do you find the location of an equivalent point load of a distributed force.

Answer 10

It is through the centroid of the shape.

Question 11

What does a Dot product do?

Answer 11

It allows you to find the angle between vectors. You can also project a vector onto another.

Question 12

What does a cross product do?

Answer 12

Finds the plane perpendicular to the given.

Question 13

What is a moment?

Answer 13

A tendency to create rotation.

Question 14

How do you calculate a moment?

Answer 14

M = F x perpendicular distance

Question 15

What is the sign convention for moments?

Answer 15

CCW is positive and CW is negative.

Question 16

What is resolving a force couple?

Answer 16

Turning many forces and moments into one of each for the same result.

Question 17

What is a unit vector?

Answer 17

A vector divided by the magnitude to show only direction.

Question 18

What do degrees of freedom describe?

Answer 18

The state of an object. Aka the position and orientation in space.

Question 19

How many degrees of freedom do 2D object have.

Answer 19

3. X, Y, and Theta Z

Question 20

How many degrees of freedom do 3D object have?

Answer 20

6. X, Y, Z, Theta X, Theta Y, Theta Z

Question 21

What does it mean when one degree of freedom is unrestricted?

Answer 21

The body is unstable.

Question 22

What does it mean when something is in static equilibrium?

Answer 22

There no net forces or torques. All degrees of freedom are also restricted.

Question 23

What are the support reactions for a pin?

Answer 23

Ry and Rx

Question 24

What are the support reactions for a roller?

Answer 24

Ry

Question 25

What are the support reactions for a fixed/cantilever?

Answer 25

Rx, Ry, M

Question 26

What are equilibrium equations?

Answer 26

Sum of forces in X, Y, Z and Sum of Moments are 0

Question 27

Explain the difference between internal and external forces on structures.

Answer 27

Internal are between members and external are between the whole structure and the environment.

Question 29

Why should you begin analysis of a structure with determining if it is a truss or not?

Answer 29

Trusses have different methods of analysis than frames or machines.

Question 30

How do you determine if a structure is a truss?

Answer 30

If any members are not two force members, if any part moves, if any part has more than two forces.

Question 31

How can you tell if a member is a two force member?

Answer 31

The member only has forces in two locations that are equal, opposite, and collinear.

Question 32

How can you use two force members?

Answer 32

If you know one end’s force, you know the other.

Question 33

What are the steps for analyzing a truss?

Answer 33

1) Determine if it’s a truss 2) Find exterior reactions 3) Use method of sections or joints

Question 34

What are the steps for Method of Joints?

Answer 34

1) Label members & joints 2) Find external forces/reactions 3) Draw FBD for each joint 4) Write and solve equilibrium equations for each point

Question 35

What are the steps for Method of Sections?

Answer 35

1) Label Members and joints 2) Solve external forces/reactions 3) Cut truss into sections doesn’t have to be a straight line, but do as few members as possible 4) Draw FBD for each section 5) Write and solve equilibrium equations for each section

Question 36

What is static friction?

Answer 36

It is the max value of friction. If it overcome, the body will move.

Question 37

What is the static friction equation?

Answer 37

Ff = Friction coefficient x Normal Force