Answer:
Angular acceleration, 
Explanation:
It is given that,
Mass of the solid sphere, m = 245 g = 0.245 kg
Diameter of the sphere, d = 4.3 cm = 0.043 m
Radius, r = 0.0215 m
Force acting at a point, F = 0.02 N
Let
is its angular acceleration. The relation between the angular acceleration and the torque is given by :

I is the moment of inertia of the solid sphere
For a solid sphere, 





So, its angular acceleration is
. Hence, this is the required solution.
To solve the problem, start by applying the concepts related to current in an RL circuit. The current is defined exponentially and using Ohm's law we can put the initial current in terms of the voltage and resistance. Consecutively with the calculated time constant we can find the respective inductance. For the second part we will apply the electrical potential energy connectors to find the amount of stored energy.
PART A)





Inductance can be defined then,



PART B) Now the energy is given under the terms:



Therefore the energy stored in the coil at this same moment is 0.0002727J
Answer:
3272.4 Hz
Explanation:
L = 31 mH
XL = 637 ohm
XL = 2 π f L
f = XL / (2 π L)
f = 637 / ( 2 x 3.14 x 31 x 10^-3)
f = 3272.4 Hz