It is in equilibrium if its velocity is not changing.
Answer:
Rotational inertia of the object is, 
Explanation:
Given that,
Mass of the object, m = 20 kg
Torsion constant of the wire, K = 0.85 N-m
Number of cycles, n = 69
Time, t = 66 s
To find,
The rotational inertia of the object.
Solution,
There exists a relationship between the moment of inertia, time period and the torsion constant of the spring is given by :

Here I is the moment of inertia
T is the time period, and it is equal to the number of cycles per unit time



So, the rotational inertia of the object is
.
Explanation:
An endothermic reaction is a type of of chemical reaction in which energy is absorbed from the surrounding. The temperature of the surrounding decreases.
An Exothermic reaction is a type of of chemical reaction in which energy is released into the surrounding. The temperature of the surrounding increases.
a)When an endothermic reaction takes place in test tube the temperature of the surrounding(here the outside wall of the test tube) will decrease which can be felt by touching the outside of the test tube.
b) Burning a candle
,Lighting a gas stove and running a car's engine all are example of exothermic reaction because energy is releases into surroundings. Where as using an instant cold pack is an example endothermic reaction in which energy is absorbed from the surrounding.
c) The diagram is of an exothermic reaction because the energy of the reactants is higher than the energy of the products.The difference in the energies of these two is the energy which was being released on completion of reaction.