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Four Types of Internal Forces
An internal force is a force that acts from within the structure.
Let us look at four types of internal forces.
Compression is a pushing force that squeezes a material.
This force often makes materials shorter.
Example: Squeeze a sponge in your hand. You are creating compression.
Tension is a pulling force that stretches a material. This force often makes materials longer.
Example: Hold one end of an elastic band in each hand. Move your hands farther apart. You are creating tension that stretches the elastic band.
Torsion is a twisting or turning force.
Example: To wring out a wet washcloth, you use the twisting force of torsion. You hold the washcloth in two hands and twist it in opposite directions to force out the water.
Bending is a force that makes a straight material curved. One side of the material squeezes together (compression). The other side stretches apart (tension).
Example: A soft or damp sponge is easy to bend. Hold it in both hands and bend it in the same way as shown in the diagram. Tension acts on the top side and compression acts on the bottom side.
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1. Match the definition to the correct term.
- a force that acts from within the structure
- a pushing force that squeezes a material
- is a pulling force that stretches a material
- is a twisting or turning force
- is a force that makes a straight material curved
2. Ling loves sleeping on her new mattress. Her old mattress was as hard as a board. The new mattress sinks comfortably under her when she climbs into bed.
What type of internal force acts on the mattress when she lies on it?CorrectIncorrect
3. Rick tunes his guitar. Rick tightens a guitar string to make it play in tune. To tighten it, he turns the tuning peg at the end of the guitar string.
What type of internal force acts on the tuning peg?CorrectIncorrect
4. Maria and her brother Marco are making a fall wreath for their door. The first step is to take a straight piece of wire and make it into a circle.
What type of internal force acts on the wire as they make it into a circle?CorrectIncorrect
5. Mr. Green is fishing and a big fish has taken the bait. The fish tries to swim away as Mr. Green tries to reel it in.
What type of internal force acts on the fishing line?CorrectIncorrect