Question

Consider a stack of six (6) pancakes. Assume that each pancake has a volume 1/4 cup (60 mL) and that the density is about 0.50g/ml . Consider the pancake at the bottom of the stack. In the sequence of questions below you will calculate the stress overall compression on the bottom pancake.

* Assume that the pancakes are roughly the same size and each are a circle with a radius of 5 cm. What is the height of each pancake? Your answer should be in cm. ans=0.764

What is the total weight (as a force in N) of pancakes sitting on top of it? Express your answer in Newtons and use g=10 m/s^2. =1.5

a) Given the information above, what is the stress applied to the bottom pancake? Your answer should be in N/m^2

Assume that the pancakes have an elastic modulus of 12,000 N/m2.

a) By how much is the bottom pancake compressed? (Your answer should be in cm).

The result above is very small and can not be easily observed. Suppose instead a 1 kg weight is placed on the entire stack of pancakes. Now the stack should be noticeable compressed.

Now what is the stress on the pancake stack?

Take the total height of the stack of 6 pancakes to be 4.5 cm. You observe that the pancakes are compressed to a height of 4 cm when the weight is added.

a) Calculate the strain in the pancakes.

b) What is the Elastic modulus for the pancakes?

The elasticity of the pancakes comes from the gluten in the flour. The interaction energy between the gluten molecules is about 4 x 10-19 J. Given that and the elastic modulus you calculated, you should be able to find the bond distance between the gluten molecules.

a) What is the bond distance between the gluten molecules? Your answer should be in meters.

Gluten Free Pancakes: Gluten free pancakes are much softer. A stack of gluten free pancakes is on 4 cm high and you use a 0.9 kg weight to compress it to 3 cm. Follow the process above to calculate the elastic modulus of these of these pancakes.

a) What is the elastic modulus of the gluten free pancakes? Your answer should be in N/m^2

The elasticity in gluten free pancakes comes from a molecular bond that is about 10 times strong than that of gluten, 4x10-18 J.

a) What is the distance of the molecular bond in gluten free pancakes?

Answer 1