Complete Question
The complete question is shown on the first uploaded image
Answer:
The work done by the spring is = 
Explanation:
Force = torque × length
Given
F = 9.13 N
length (L) = 5.91 cm = 0.0591 m [Note 1 m = 100 cm ]
considering the formula above
where k denotes torque

Energy Stored 

Answer:
a) 3.9 x 10⁻⁵ kg
Explanation:
The amount of mass required to produce the energy can be given by Einstein's formula:

where,
m = mass required = ?
E = Energy produced = 3.5 x 10¹² J
c = speed of light = 3 x 10⁸ m/s
Therefore,

Hence, the correct option is:
<u>a) 3.9 x 10⁻⁵ kg</u>
Answer:
option (D) is correct.
Explanation:
According to the work energy theorem, the work done by all forces is equal to the change in kinetic energy of the body.
the kinetic energy of a body is directly proportional to the square of the speed of the body.
As the kinetic energy change, the speed of the body also change.
Option (D) is correct.