04 - Commen specialist technical priciples Flashcards
what is a static load/force?
a force which does not move
what is a dynamic load/force?
a force that moves
give an example of a static load
a book edging on a table top
give an example of a dynamic load
a book dropped from a roof falling onto a table
when does tension occur?
when a pulling force is applied to either end of a material
what happens when an object is under tension?
it becomes stretched
give two examples of tension
- the rope during a tug of war
- chains supporting a swing
define tensile strength
the ability of an object to resist being pulled apart
when does compression occur?
when a pushing force is applied to either end of a material (opposite to tension)
give 3 examples of objects under compression
- spring in a suspension system
- clove of garlic in a garlic press
- air in a spray deodorant
why is holding liquids and gases under compression an economical way of storing them?
- take up less room
- can easily control their release (through valves)
define compressive strength
the ability of a material to resist being compressed or squashed
when does torsion occur?
when two ends of the material rotate in opposite directions
give 2 examples of objects under torsion
- wringing a wet towel
- boats riding over waves
what is torsional strength?
the ability of a material to resist being twisted out of shape
describe a bending force
- results in both tension and compression (stop think for a minute how)
- top is tension
- underside is compression
how is a bending force applied?
- applied to both sides with either upward or downward pressure
define stiffness
the ability of a material to resist being bent out of shape
describe the direction on a shear force
acts on an object in a perpendicular direction to the length
give an example of a shear force
- wind pushing against a tree
describe shear forces in terms of joints
materials being pulled apart along different planes or lines (travel in opposite directions)
