Answer:
The angular velocity is ![w = 53.35 \ rounds /minute](https://tex.z-dn.net/?f=w%20%3D%2053.35%20%5C%20rounds%20%2Fminute)
Explanation:
From the question we are told that
The mass of the block is ![m = 61.2kg](https://tex.z-dn.net/?f=m%20%3D%2061.2kg)
The of the pulley is ![M = 14.2 kg](https://tex.z-dn.net/?f=M%20%3D%2014.2%20kg)
The radius of the pulley is
The radius of the cord around the pulley is ![r = 1.5 m](https://tex.z-dn.net/?f=r%20%3D%201.5%20m)
The distance of the block to the floor is ![d = 8.0 m](https://tex.z-dn.net/?f=d%20%3D%208.0%20m)
From the question we are told that the moment of inertia of the pulley is
![I = \frac{1}{2} MR^2 kg \cdot m^2](https://tex.z-dn.net/?f=I%20%20%3D%20%5Cfrac%7B1%7D%7B2%7D%20MR%5E2%20kg%20%5Ccdot%20m%5E2)
Substituting value
![I = \frac{1}{2} * 14.2 * (1.5)^2](https://tex.z-dn.net/?f=I%20%3D%20%5Cfrac%7B1%7D%7B2%7D%20%20%2A%2014.2%20%2A%20%281.5%29%5E2)
![I = 15.975 kg \cdot m^2](https://tex.z-dn.net/?f=I%20%3D%2015.975%20kg%20%5Ccdot%20m%5E2)
Using the Newtons law we can express the force acting on the vertical axis as
![ma = mg -T](https://tex.z-dn.net/?f=ma%20%3D%20mg%20-T)
=> ![T = mg -ma](https://tex.z-dn.net/?f=T%20%3D%20mg%20-ma)
Now when the pulley is rotated that torque generated on the massless cord as a r result of the tension T and the radius of the cord around the pulley is mathematically represented as
![\tau = I \alpha](https://tex.z-dn.net/?f=%5Ctau%20%3D%20I%20%5Calpha)
Here
is the angular acceleration
Here
is the torque which can be equivalent to
![\tau = T r](https://tex.z-dn.net/?f=%5Ctau%20%3D%20T%20r)
Substituting this above
Substituting for T
![(mg - ma ) r = I\ r \alpha](https://tex.z-dn.net/?f=%28mg%20-%20ma%20%29%20r%20%3D%20%20I%5C%20%20r%20%5Calpha)
Here
is the linear acceleration which is mathematically represented as
![a = r\alpha](https://tex.z-dn.net/?f=a%20%3D%20r%5Calpha)
![(mg - m(r\alpha ) ) r = I\ r \alpha](https://tex.z-dn.net/?f=%28mg%20-%20m%28r%5Calpha%20%29%20%29%20r%20%3D%20%20I%5C%20%20r%20%5Calpha)
![mgr = I\alpha + m(r\alpha ) r](https://tex.z-dn.net/?f=mgr%20%3D%20I%5Calpha%20%20%2B%20m%28r%5Calpha%20%29%20r)
![mgr = \alpha [ I + mr^2]](https://tex.z-dn.net/?f=mgr%20%3D%20%5Calpha%20%20%5B%20I%20%2B%20mr%5E2%5D)
making
the subject
Substituting values
![\alpha = \frac{61.2 * 1.5 * 9.8}{15.975 + (61.2 ) * (1.5)^2}](https://tex.z-dn.net/?f=%5Calpha%20%20%3D%20%5Cfrac%7B61.2%20%2A%201.5%20%2A%209.8%7D%7B15.975%20%2B%20%2861.2%20%29%20%2A%20%281.5%29%5E2%7D)
![\alpha =5.854 rad /s^2](https://tex.z-dn.net/?f=%5Calpha%20%3D5.854%20rad%20%2Fs%5E2)
Now substituting into the equation above to obtain the acceleration
![a = 5.854 * 1.5](https://tex.z-dn.net/?f=a%20%3D%205.854%20%2A%201.5)
![a=8.78 m/s^2](https://tex.z-dn.net/?f=a%3D8.78%20m%2Fs%5E2)
This acceleration is ![a = \frac{v}{t}](https://tex.z-dn.net/?f=a%20%3D%20%5Cfrac%7Bv%7D%7Bt%7D)
and v is the linear velocity with is mathematically represented as
![v = \frac{d}{t}](https://tex.z-dn.net/?f=v%20%3D%20%5Cfrac%7Bd%7D%7Bt%7D)
Substituting this into the formula acceleration
![a = \frac{d}{t^2}](https://tex.z-dn.net/?f=a%20%3D%20%5Cfrac%7Bd%7D%7Bt%5E2%7D)
making t the subject
![t = \sqrt{\frac{d}{a} }](https://tex.z-dn.net/?f=t%20%3D%20%5Csqrt%7B%5Cfrac%7Bd%7D%7Ba%7D%20%7D)
substituting value
![t = \sqrt{\frac{8}{8.78}}](https://tex.z-dn.net/?f=t%20%3D%20%5Csqrt%7B%5Cfrac%7B8%7D%7B8.78%7D%7D)
![t = 0.9545 \ s](https://tex.z-dn.net/?f=t%20%3D%200.9545%20%5C%20s)
Now the linear velocity is
![v = \frac{8}{0.9545}](https://tex.z-dn.net/?f=v%20%3D%20%5Cfrac%7B8%7D%7B0.9545%7D)
![v = 8.38 m/s](https://tex.z-dn.net/?f=v%20%3D%208.38%20m%2Fs)
The angular velocity is
![w = \frac{v}{r}](https://tex.z-dn.net/?f=w%20%3D%20%5Cfrac%7Bv%7D%7Br%7D)
So
![w = \frac{8.38}{1.5}](https://tex.z-dn.net/?f=w%20%3D%20%5Cfrac%7B8.38%7D%7B1.5%7D)
![w = 5.59 rad/s](https://tex.z-dn.net/?f=w%20%3D%205.59%20rad%2Fs)
Generally 1 radian is equal to 0.159155 rounds or turns
So 5.59 radian is equal to x
Now x is mathematically obtained as
![x = \frac{5.59 * 0.159155}{1}](https://tex.z-dn.net/?f=x%20%3D%20%5Cfrac%7B5.59%20%2A%200.159155%7D%7B1%7D)
![= 0.8892 \ rounds](https://tex.z-dn.net/?f=%3D%200.8892%20%5C%20rounds)
Also
60 second = 1 minute
So 1 second = z
Now z is mathematically obtained as
![z = \frac{ 1}{60}](https://tex.z-dn.net/?f=z%20%3D%20%5Cfrac%7B%201%7D%7B60%7D)
z ![= 0.01667 \ minute](https://tex.z-dn.net/?f=%3D%200.01667%20%5C%20minute)
Therefore
![w = \frac{0.8892}{0.01667}](https://tex.z-dn.net/?f=w%20%3D%20%5Cfrac%7B0.8892%7D%7B0.01667%7D)
![w = 53.35 \ rounds /minute](https://tex.z-dn.net/?f=w%20%3D%2053.35%20%5C%20rounds%20%2Fminute)