Rest - it is the state in which body doesn’t move from it’s place
motion - it is the state in which body moves from it’s place
We know that momentum = mass times velocity
So a. 720 kgm/s
Here we can use momentum conservation as in this type of collision there is no external force on it

now here we can say




now here we can say


now by coefficient of restitution
for elastic collision we know that e = 1


now by solving the two equation


also we know that

so final speed of the nail is 6.875 m/s
Answer:
Yes , it is possible for two different atoms of carbon to have different numbers of neutrons in their nuclei .
Explanation:
Isotopes -
Atoms of the element with same number of the electrons and protons , but differ in the number of neutrons , are called as the isotopes .
The isotopes of the element have the same number of protons and electrons , hence have the same chemical and physical properties .
Many isotopes occurs naturally .
In case of Carbon ,
Carbon too have isotopes ,
i.e.
Carbon - 13 and Carbon - 14
carbon - 13 , have seven neutrons
Carbon - 14 , have eight neutrons .