FORCES

V. Ryan © 2002 - 2015

There are different types of forces that act in different ways on structures such as bridges, chairs, buildings, in fact any structure. The main examples of forces are shown below. Study the diagram and text and then draw a diagram/pictogram to represent each of these forces.

A Static Load : A good example of this is a person seen on the left. He is holding a stack of books on his back but he is not moving. The force downwards is STATIC.

A Dynamic Load : A good example of a dynamic load is the person on the right. He is carrying a weight of books but walking. The force is moving or DYNAMIC.

Internal Resistance : The person in the diagram is sat on the mono-bicycle and the air filled tyre is under great pressure. The air pressure inside it pushes back against his/her weight.

Tension : The rope is in “tension” as the two people pull on it. This stretching puts the rope in tension.

INTERNAL RESISTANCE

TENSION

Compression : The weight lifter finds that his body is compressed by the weights he is holding above his head.

Shear Force : A good example of shear force is seen with a simple scissors. The two handles put force in different directions on the pin that holds the two parts together. The force applied to the pin is called shear force.

COMPRESSION

SHEAR FORCE

Torsion : The plastic ruler is twisted between both hands. The ruler is said to be in a state of torsion.

TORSION

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