Find the false statement:
a. Linear polymers are typically more ductile than cross-linked polymers at the cost of less strength
b. Higher strain rate often makes the polymer more brittle
c. Relaxation modulus is a representative of stress drop with respect to the initial stress
d. An elastomer have some cross-linking but not as the thermosets

Option (c) is the correct answer.

Explanation:

Due to the structure of linear polymers they are highly ductile in nature. And, more is the number of strains present in a polymer more will be its brittleness.

Time dependent stress with respect to some strain level measure remains constant is known as relaxation modulus.

Mathematically,  

More cross-linking is present in thermosets whereas there is low degree of cross-linking in elastomers. Therefore, it means that an elastomer will have some amount of cross-linking but not as thermosets.

Thus, we can conclude that the statement relaxation modulus is a representative of stress drop with respect to the initial stress, is false.

Vix = R / Cos angle = 86.75 x cos 42.2 =117.1 m/s

Fc =m V<2 / r  = 7.30 x (117.1)<2 / 1.67 = 59940.47 N