Answer:
The fraction fraction of the final energy is stored in an initially uncharged capacitor after it has been charging for 3.0 time constants is

Explanation:
From the question we are told that
The time constant 
The potential across the capacitor can be mathematically represented as

Where
is the voltage of the capacitor when it is fully charged
So at


Generally energy stored in a capacitor is mathematically represented as

In this equation the energy stored is directly proportional to the the square of the potential across the capacitor
Now since capacitance is constant at
The energy stored can be evaluated at as


Hence the fraction of the energy stored in an initially uncharged capacitor is

Given :
Two forces act on a 6.00-kg object. One of the forces is 10.0 N.
Acceleration of object 2 m/s².
To Find :
The greatest possible magnitude of the other force.\
Solution :
Let, other force is f.
So, net force, F = 10 + f.
Now, acceleration is given by :

Therefore, the greatest possible magnitude of the other force is 2 N.
Hence, this is the required solution.
Answer:
B. over the symbol.
Explanation:
vectors are represented with a symbol carrying an arrow head with also indicates direction
As per Newton's III law every action has equal and opposite reaction
So here we can say that
every body which apply force on other body must have a reaction force of same magnitude in opposite direction
So here if ball hits the ground by 50 N force then the ball must have a reaction force on itself with same magnitude and opposite direction
the magnitude of the force will be 50 N
and its direction is opposite to the force that ball apply on the floor