Answer:
The speed of the heavier fragment is 0.335c.
Explanation:
Given that,
Mass of the lighter fragment 
Mass of the heavier fragment 
Speed of lighter fragment = 0.893c
We need to calculate the speed of the heavier fragment
Let v is the speed of the second fragment after decay
Using conservation of relativistic momentum













Hence, The speed of the heavier fragment is 0.335c.
Answer:

Explanation:
q = Charge in the potassium ion = 
e = Charge of electron = 
= Change in potential = 
Change in electric potential is given by

The energy is 
Answer:
E) d/sqrt2
Explanation:
The initial electric force between the two charge is given by:

where
k is the Coulomb's constant
q1, q2 are the two charges
d is the separation between the two charges
We can also rewrite it as

So if we want to make the force F twice as strong,
F' = 2F
the new distance between the charges would be

so the correct option is E.