C) because a new substance is formed
B) not sure but might be because the chemical properties of the substance has changed
To solve the problem it is necessary to apply the concepts given in the kinematic equations of angular motion that include force, acceleration and work.
Torque in a body is defined as,

And in angular movement like

Where,
F= Force
d= Distance
I = Inertia
Acceleration Angular
PART A) For the given case we have the torque we have it in component mode, so the component in the X axis is the net for the calculation.

On the other hand we have the speed data expressed in RPM, as well


Acceleration can be calculated by



In the case of Inertia we know that it is equivalent to


Matching the two types of torque we have to,




PART B) The work performed would be calculated from the relationship between angular velocity and moment of inertia, that is,



The answer is a White Dwarf.
Answer:
At the highest point the velocity is zero, the acceleration is directed downward.
Explanation:
This is a free-fall problem, in the case of something being thrown or dropped, the acceleration is equal to -gravity, so -9.80m/s^2. So, the acceleration is never 0 here.
I attached an image from my lecture today, I find it to be helpful. You can see that because of gravity the acceleration is pulled downwards.
At the highest point the velocity is 0, but it's changing direction and that's why there's still an acceleration there.