Answer:
a)
, b) 
Explanation:
a) The final velocity of the 13.5 g coin is found by the Principle of Momentum Conservation:

The final velocity is:

b) The change in the kinetic energy of the 13.5 g coin is:
![\Delta K = \frac{1}{2}\cdot (13.5\times 10^{-3}\,kg)\cdot \left[(11.9\times 10^{-2}\,\frac{m}{s} )^{2}-(0\,\frac{m}{s} )^{2}\right]](https://tex.z-dn.net/?f=%5CDelta%20K%20%3D%20%5Cfrac%7B1%7D%7B2%7D%5Ccdot%20%2813.5%5Ctimes%2010%5E%7B-3%7D%5C%2Ckg%29%5Ccdot%20%5Cleft%5B%2811.9%5Ctimes%2010%5E%7B-2%7D%5C%2C%5Cfrac%7Bm%7D%7Bs%7D%20%29%5E%7B2%7D-%280%5C%2C%5Cfrac%7Bm%7D%7Bs%7D%20%29%5E%7B2%7D%5Cright%5D)

Answer:
B. Axial stress divided by axial strain
Explanation:
Elasticity:
It is the tendency of an object to deform along the axis when an opposing force is applied without facing permanent change in shape.
Plasticity:
When an object crosses the elasticity limit, it enters plasticity where the change due to stress is permanent and the object might even break.
Yield strength:
Yield strength is the point of maximum bearable stress that indicates the limit of elasticity.
Our case:
As the stress applied is less than the yield strength, the rod is still in the elasticity state and its modulus can be calculated.
Modulus of Elasticity = Stress along axis/Ratio of change in length to original length
Axial strain is basically the ratio of change in length to original length.
So, Modulus of Elasticity = Axial Stress/ Axial Strain