Rubber Band Lab

Big Questions:
"How can we store energy to do work for us later?"
"How does the force it takes to stretch a rubber band depend on the AMOUNT by which you stretch it?"

 ~ This week we performed a lab where we measured the amount of force needed to stretch the rubber band a certain distance. With the electronic force probe, we pulled the rubber band for a variety of distances. At first we measured the force needed to stretch a single-banded rubber band. Then we double-banded it and repeated the steps.

     Single-banded Rubber Band Data:

     0.01 m: 0.538 N
     0.02 m: 1.341 N
     0.03 m: 1.710 N
     0.04 m: 2.693 N
     0.05 m: 3.372 N

     Elastic Constant: 70.85 N/m

     Double-banded Rubber Band Data:

     0.01 m: 3.835 N
     0.02 m: 6.375 N
     0.03 m: 8.605 N
     0.04 m: 11.313 N
     0.05 m: 12.782 N

     Elastic Constant: 223.675 N/m

 ~ We see that as the distance of the stretch increased, the amount of force needed increased as well. Also, as we stretch the rubber band, it has potential energy. We acquired the elastic constant by graphing our data. By drawing the best-fit line through the points, we can find the slope (elastic constant). We can derive two equations from this: Fs=kx (Hooke's Law) and Us=1/2kx squared. Us=1/2kx squared is the equation for elastic potential energy.

      We got Fs=kx from the y=mx+b. We substitued Fs (force) for y and the slope k (elastic constant) for m.

      The second equation is acquired from the equation for the area of the triangle. The equation of the area is A=1/2b•h. We substitued Us for A, x (distance) for b, kx (force) for h.

Slingshots

     

To use a slingshot, you must pull the sling back as far as you can to get maximum distance and speed. By pulling it back, there is potential energy. It is then transferred to the object in the sling when you release it.