A cylindrical pulley with a mass of 8 kg, radius of 0.561 m and moment of inertia 1 2 M r2 is used to lower a bucket with a mass of 1.9 kg into a well. The bucket starts from rest and falls for 2.6 s. r M m How far does it drop

Respuesta :

Answer:

s = 15.84m

Explanation:

In order to calculate the distance traveled by the bucket, you first use the formula for the torque exerted on the pulley by the weight of the bucket:

[tex]\tau=I\alpha[/tex]        (1)

I: moment of inertia of the pulley

α: angular acceleration of the pulley

You can calculate the angular acceleration by taking into account that the torque is also:

[tex]\tau=Wr[/tex]     (2)

W: weight of the bucket = Mg = (1.9kg)(9,8m/s^2) = 18.62N

r: radius of the pulley = 0.561m

[tex]\tau=(18.62N)(0.561m)=10.44Nm[/tex]

The moment of inertia is given by:

[tex]I=\frac{1}{2}M_pr^2[/tex]     (3)

Mp: mass of the pulley = 8kg

[tex]I=\frac{1}{2}(8kg)(0.561m)^2=1.25kg.m^2[/tex]

You solve the equation (1) for α and replace the values of the moment of inertia and the torque to obtain the angular acceleration:

[tex]\alpha=\frac{\tau}{I}=\frac{10.44Nm}{1.25kgm^2}=8.35\frac{rad}{s^2}[/tex]

Next, you use the following formula to find the angular displacement:

[tex]\theta=\frac{1}{2}\alpha t^2[/tex]

[tex]\theta=\frac{1}{2}(8.35rad/s^2)(2.6s)^2=28.24rad[/tex]

Finally, you calculate the arc length traveled by the pulley, this arc length is equal to the vertical distance traveled by the bucket:

[tex]s=r\theta =(0.561m)(28.24rad)=15.84m[/tex]

The distance traveled by the bucket is 15.84m