How do tension and compression work together

A compression force is one that squeezes material together. Some materials are better able to withstand compression, some are better able to resist tension, and others are good to use when both compression and tension are present. For example, if you pull on a strong rope, it can support a large amount of tension. If you push on a rope, it cannot resist compression very well, and just bends.

Marshmallows are an example of a material that is easily compressible, but pulls apart under a great amount of tension.

From these examples, it is clear that materials may bend or stretch when under a compressive or tensile force. Refer to the associated activity Leaning Tower of Pasta for students to illustrate these forces by building their own structures using spaghetti and marshmallows. When two people sit on a seesaw, is the metal bar between the two seats experiencing compressive or tensile stress?

This is a trick question! A "bar in bending" experiences both compressive and tensile stresses! To visualize this, grab a paperback book and bend it down see Figure 1. When you do this, the book materials "want" to return to their normal state of rest, so it feels like the top pages try to pull your fingers together because they are in tension and the bottom pages push your fingers apart because they are in compression.

The bending book experiences compressive and tensile stress, just like a seesaw bar that is being bent! Figure 1. A demonstration using a phone book illustrates tensile and compressive stresses due to bending; the top pages stretch apart tension and the bottom pages push together compression.

With the bending book, the greatest tensile and compressive stresses occur on the outer covers; the direction of these forces can be seen with the red arrows in Figure 1. The neutral axis or layer runs along the middle of the book between the red arrows, as if it was the middle page in the book. Amazingly, this axis experiences zero stresses while bending!

This has practical applications. For example, if you ever need to drill a hole in a support beam, like the ones along the ceiling in your basement, drill in the center of the beam where there are no stresses see Figure 2. Figure 2. A diagram that shows the effect of a heavy weight placed on a beam.

The beam experiences tension and compression. If the weight is too big, the beam will break! The diagram in Figure 2 shows the effect on the beam when a heavy weight is placed on it, causing both tension and compression in the beam. The weight causes compression on the top of the beam as it squeezes together, and causes tensile stress on the bottom side of the beam where it is pulled apart.

The beam shortens on the top due to compression, and elongates on the bottom due to tension. With this in mind, what would happen if the beam had an even heavier weight placed on it? In this case, the forces would exert a greater amount of tension and compression on the beam, and if the forces were too great, the material would not be able to handle the stress and it would break in half.

Tension and compression forces are important to keep in mind when designing a building or structure. If we construct a bridge with materials that are not strong enough to hold up to the amount of compression and tension that vehicles cause when they travel across it, the bridge could collapse! All structures must be able to handle the forces that act upon them, or they would not stay up.

A great deal of science, design and engineering goes into predicting the kinds of loads a structure might encounter for example, wind, snow, weight of a bathtub full of water, etc. For example, houses and bridges built in California must be designed to withstand earthquakes. Some materials snap when there is a load on them. These materials — such as ice — are brittle.

Would you be able to safely walk across a river when it had just frozen over? Probably not, because the layer of ice is thin and would likely crack. Because ice is brittle, a thin layer would not be able to resist the compression and tension caused by your weight and movement. But what if you crossed the river once the ice had become half a meter thick? At this point, the ice is able to resist the tension and compression, even though it is still brittle.

The strength of a structure is a function of both its materials and its size. These concepts of material properties and size are considered when building bridges for vehicles to travel over. For example, suspension bridges, such as the Golden Gate Bridge in San Francisco, use steel wire wrapped together to make it so strong that a diameter of just 1cm is strong enough to hold 8, kg of weight two full grown elephants!

Why do you think people design and build enormous, tall buildings? Q'eswachaka is an important example of sustainability from environmental and engineering perspectives. The bridge is built of strong, locally harvested, and fully biodegradable materials. The Inka understood the characteristics of a variety of fibrous materials such as grass, cotton, and llama and other camelid wool. So, it was natural for the Inka to find an engineering solution using a locally abundant grass fiber that could be woven to make rope.

Individual grass fibers can break and tear easily, but twisting and braiding them yields a stronger and more flexible material. This is because strength increases with more elements to share the load, or the forces, acting on them. In suspension bridges, including Q'eswachaka, cables work through tension, or the stress resulting from a pulling force. However, if you pull a cable too much, it will break. The Inka understood this and used the engineering concept of tensile strength.

The tensile strength of the grass cables, or how much they can be pulled from opposite directions before they break, is critical. The bridge builders also knew how much the cables could be stretched by the weight of the expected foot traffic on the bridge. This is the reason Concrete is strong in compression and very weak in tension. IS Plain and Reinforced Concrete — Code of Practice is an Indian Standard code of practice for general structural use of plain and reinforced concrete.

The latest revision of this standard was done in year , reaffirmed It gives extensive information on the various aspects of concrete. Concrete is made by mixing Cement, Sand, water, and aggregate. Due to the applied pull force, the glue which holds different constituents of concrete together will break.

So under tension, this zone will act as a weak link and concrete will fail at a lower force. Material Properties Concrete may be referred to as a brittle material. Begin typing your search term above and press enter to search. Press ESC to cancel. Skip to content Home Physics How do tension and compression work together? It's the job of the bridge design to handle these forces without buckling or snapping.

Buckling occurs when compression overcomes an object's ability to endure that force. Snapping is what happens when tension surpasses an object's ability to handle the lengthening force. The best way to deal with these powerful forces is to either dissipate them or transfer them. With dissipation, the design allows the force to be spread out evenly over a greater area, so that no one spot bears the concentrated brunt of it. It's the difference in, say, eating one chocolate cupcake every day for a week and eating seven cupcakes in a single afternoon.

In transferring force, a design moves stress from an area of weakness to an area of strength.