Building Bridges to Support Weight

Big Idea: How are bridges built? How can they support weight?

Focus question: How do scientists build bridges to support lots of weight?

Prediction:

·        If we use more index cards, it will support more weight because it will provide a thicker base that supports more weight.

·        If we cut the cards into thirds and stack them, they will be thicker and support more weight.

·        If the bridge (cards) do not have enough support (markers), the bridge will fall down.

Planning:

Materials:  markers, large and small washers, pennies flat surface

First, we cut our index cards into thirds. Then, we stood five of our markers up to represent as our supports for the bridge. Then, we put a stack of three index cards over the markers. Next, we put a washer in each corner. Then, we added some small ones and then larger ones in the middle of our bridge to determine its ability to support weight. Finally, we tested a different way with less markers and less weights in the middle of the bridge.

Data :

Test 1                                  Test 2

                 

Test 3                                   Test 4

In the first picture, we used five markers to support our bridge, one in each corner and one in the middle. We added three index cards cut into thirds to the top of the markers for our bridge. Then, we tested weights to see if our bridge could hold the weight, a few small washers at a time. In the first picture, four small washers, one in each corner was supported by our bridge. In the second picture, using the same bridge, we added three more small washers to test our bridge. It still held the weight. In the third picture, we added two pennies each to opposite corners and two large washers in the middle of previous bridge. Our bridge still held the weight and we determined our bridge to be built to hold a lot of weight. The last picture we wanted to try something different so we used three markers in a triangle set up, three stacks of index cards cut into thirds on top, and three large washers on top of the bridge. This bridge also held a larger amount of weight.

Claims and evidence:

We claim that using more index cards is equivalent to using material of the bridge that is thicker because it will support more weight because it will provide a thicker base that supports more weight. We know this because when we stacked our index cards three high, it provided more support for more weight that we continued to add to test our hypothesis. We claim that when you cut the cards into thirds and stack them, they will be thicker and support more weight. We know this to be true because that is what we did to have more index card material to use for our bridge and it made our bridge support more weight. We claim that if the bridge (cards) do not have enough support (markers), the bridge will fall down. We know this to be true because we used five markers in position for each corner of the index card including the middle, and the cards did not fall down.

Conclusion:

We learned that the material used to make the bridge is just as important as the support for the bridge in that they both need to be made strong to support a lot of weight. We also learned that position is important for support. In our first test, we put markers at every angle and in the center which gave a balance of support. In the last test, we put three markers in the middle in a triangle position, three index cards on top and three washers on top of the index cards and in the middle. This weight was supported. If we had put the washers to the outer edge of the index cards, there would have been no weight underneath for support. It would have collapsed. Our first test, when we put the weights in every corner and throughout the middle, it did not collapse and remained sturdy. From this evidence, we claim that scientists build bridges to support lots of weight by using material that is durable and heavier than the weight will be on top. Additionally, the scientists build the bridge using supports underneath that provides a balance of weight support so no area will be unsupported.

Reflection/Questions:

We learned that the material for building bridges need to be heavy, durable, and strong to support a lot of weight.

·        What is the best types of materials to use to build a bridge that supports heavy weight?

·        I notice some bridges have signs that say the bridge will only support “x” amount of weight and some trucks are not to cross it…Why can’t scientists build the bridges to support more weight so the trucks can cross?

Literacy Connections:

Bridges:  Amazing structures to design, build, and test ( Kaleidoscope kids books (William Publishing)) by Carol A. Johnmann

You wouldn’t want to work on the Brooklyn Bridge:  An enormous project that seemed impossible by Thomas Ratliff and David Salariya