Trusses, Distributed Forces, Mechanisms and Machines

Question 1

What are the two simplifications we can make to analyse a truss?

Answer 1

1. The beams are pin jointed at their ends
2. The forces are only applied at joints

Question 2

What are the two methods we can use to solve forces in a truss?

Answer 2

Method of joints
Method of sections

Question 3

How does the methods of joints work?

Answer 3

Isolate a joint where only two beams meet, so we can solve for two unknowns using the external forces applied to the bridge. Then we can use the calculated values to find the other unknowns in the other joints.

Question 4

How does the method of sections work?

Answer 4

We can highlight a section of the truss, and then we can resolve the forces that come in and out of the section

Question 5

Why does the method of sections work?

Answer 5

Because all of the internal forces will resolve to 0N, meaning that we won’t have to calculate their values

Question 6

How can we determine where a distributed force acts?

Answer 6

We can identify how the force acts over the area, and then find the centre of the point e.g. if the force is constant over the whole area, then we can say that the force acts in the centre of the area when modelling it

Question 7

What is the resultant force of a force q acting over an area a?

Answer 7

R = qa