Science You will need your science duo-tang and pencil case for today’s science class.

Force on Structures

Tension & Compression Tension Compression

Part 1: Push & Pull Hold the straw at both ends and pull. What kind of force did you exert? Look closely at the pleated section of the straw. What does it look like? Draw a picture of what you see. Hold the straw at both ends and push it back together again. What kind of force did you exert? Look again at the pleated section of the straw. What does it look like now? Draw a picture of what you see.

Part 2: Measuring Force Two chairs about 15cm apart and lay the straw across the gap. Make sure the pleated section of the straw is over the gap. Tape the two ends of the straw to the chairs so it will not move. Put your finger on the pleated part of the straw and push down gently until the straw bends.

Part 2: Measuring Force Look at the pleated section. What does it look like? Draw a picture of what you see. What side of the straw is under tension? What side is under compression?

Part 2: Measuring Force Return the straw to its position in step 2. Make sure the pleated part of the straw is pushed together. Bend the paper clip to make a hook. Use the hook to hang the spring scale over the centre of the pleated part of the straw. Gently pull down on the spring scale. How much force did it take to bend the straw.

Communication Explain the meaning of each of these terms in your own words or with a drawing: tension, compression, bending, flexible, rigid. Look around the classroom. List 2 objects you see that are under tension and 2 objects that are under compression. What is causing the force? What forces acted on the pleated straw in Parts 1 & 2? How do you know?