Passage II
Seven 4 g mixtures of glycerol and agar were prepared, each having a different percent glycerol by mass. A plastic film was made from each mixture; all the films were rectangular and had the same dimensions.
Each film was clamped and stretched (see Figure 1) at 25°C until it broke.
Three properties of the film were determined:
• Tensile stress, the force applied per unit area of the film as the film broke
• Percent elongation, given by:
• Elastic modulus, a measure of the rigidity of the film
The results for all 7 films are shown in Figures 2 and 3.
Figures adapted from Eugene S. Stevens et al., "Polymer-Plastics Experiments for the Chemistry Curriculum." @2006by Division of Chemical Education, lnc., American Chemical Society.
9. Suppose the initial length of a certain film was 5.0 cm and the final length of the film was 6.0 cm. The percent elongation of the film was:
Your Answer is
Correct Answer is A
Explanation
Looking at the algorithm formula of percent elongation below figure 1, it can be known that percent elongation=(6-5)/5=20% from 5 cm to 6 cm