Answer:
Is the equation for Ec=1/2 m(Dv)^2 where Dv is the difference between the angular speed & the areolar speed?
I think the force of spinning it can only hold for so long and because of gravitys pressure.(i hope i helped) :)
Answer:
(a) 
(b) 
Explanation:
According to Newton's second law:

Recall that the frictional force is related jointly with the coefficient of friction and normal force
. Replacing in the above equation, we get the coefficient of friction:

(a) The coefficient of static friction is related with the force required to set the block in motion:

(b) The coefficient of kinetic friction is related with the force required to keep the block moving with constant speed:

The ability to convert voltage to and from mechanical stress.
I believe the answer is D.