For a polymer that was maintained at constant strain, an initial stress of 2.76 MPa decreases to 1.72 MPa after 6 hr. Estimate the stress remaining after 30 hr.

1.48 Mpa

Explanation:

Given that For a polymer that was maintained at constant strain, an initial stress of 2.76 MPa decreases to 1.72 MPa after 6 hr. To estimate the stress remaining after 30 hr, we must first find the decay constant by using the exponential equation.

Therefore, the estimate of the stress remaining after 30 hr, is 1.48Mpa.

Please find the attached file for the solution.

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.