Answer:
Explanation:
The equation for this is
f = μ
where f is the frictional force the block needs to overcome, μ is the coefficient of static friction, and 
(that means that the normal force is the same as the weight of the block which has an equation of weight = mass times the pull of gravity). Filling in:
1.09 = μ(.413)(9.8) and
μ = 
so
μ = .27
Answer: 20 m/s
Explanation: To solve this problem we have to consider the expression of the kinetic energy given by:
Ekinetic=(1/2)*(m*v^2)
then E=0.5*30Kg*(20 m/s)^2=15*400=6000J
The correct answer of this question is : A) Change alternating current into direct current.
EXPLANATION :
As per the question, we are given vacuum tube. Vacuum tube can be of various types. Normally it contains two electrodes called cathode and anode which are enclosed in an evacuated glass chamber . There are also other types of vacuum tubes which contain extra electrodes like control grid .
The vacuum tube can be used as a rectifier. It means that it can be used as an electronic device which will convert alternating current into direct current. It may be a half wave rectifier or a full wave rectifier. Actually the direct current obtained during the rectification of alternating current is pulsating in nature.
Hence, the correct answer is that a vacuum tube can be used to change alternating current into direct current.
