An elevator cable winds on a drum of radius 771 cm that is connected to a motor.
If the elevator moves down 8.60 m, how many revolutions has the drum made?

Respuesta :

The relationship between the length of the circle and its radius allows to find the result for the revolutions turned when the distance decreases  8.60m is:

           Angle = 17.8 rev

The length of a circle is given by the expression.

         L = 2π r

Where L is the length of the circle and r is the radius of the circle.

They indicate the radius of the drum is r = 7.71 cm = 7.71 10⁻² m, let's find the length of the circle.

         Lo = 2 π 7.71 10⁻²

         Lo = 0.4844 m

Let's find the angle that the drum has rotated, using a direct proportional rule. If rotate an angle of 2π radians when you descend 0.4844 m, what angle you rotate when you descend 8.60 m.

          #_ angles =  [tex]8.6 m \ \frac{2\pi \ rev} { 0.4844 m}[/tex]  

          #_angle = 111.55 radians

Let's reduce to revolutions.

         # _angles = 111.55 radians ( [tex]\frac{1 rev }{2\pi rad}[/tex] )

         #_angulo = 17.8 rev

In conclusion, using the relationship between the length of the circle and its radius, we can find the result for the revolutions turned when the distance decreases is:

           Angle = 17.8 rev

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