Answer:
i think its B sorry if its wrong
Answer:
(A) 2.4 N-m
(B) 
(C) 315.426 rad/sec
(D) 1741.13 J
(E) 725.481 rad
Explanation:
We have given mass of the disk m = 4.9 kg
Radius r = 0.12 m, that is distance = 0.12 m
Force F = 20 N
(a) Torque is equal to product of force and distance
So torque
, here F is force and r is distance
So 
(B) Moment of inertia is equal to 
So 
Torque is equal to 
So angular acceleration 
(C) As the disk starts from rest
So initial angular speed 
Time t = 4.6 sec
From first equation of motion we know that 
So 
(D) Kinetic energy is equal to 
(E) From second equation of motion

Answer:
72.04 dB.
Explanation:
The intensity level of 60dB corresponds to the sound intensity
given by the equation

where 
solving for
we get:



Now, when 16 violins are playing the intensity
becomes

which on the decibel scale gives

.
Thus, playing 16 violins together gives the intensity level of 72 dB.
To solve this problem it is necessary to use the conservation equations of both kinetic, rotational and potential energy.
By definition we know that

Where,
KE =Kinetic Energy
KR = Rotational Kinetic Energy
PE = Potential Energy
In this way

Where,
m = mass
v= Velocity
I = Moment of Inertia
Angular velocity
g = Gravity
h = Height
We know as well that
for velocity (v) and Radius (r)
Therefore replacing we have

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Therefore the height must be 0.3915 for the yo-yo fall has a linear speed of 0.75m/s