Question

A boy is moving a box upward through the use ofa pulley 21 cm in radius. If the pulley is rotated counterclockwise through an angle of 120, what is the height, that the weight will rise.​

Answer 1

Answer:

15m is the correct answer

Answer 2

Given:

A boy is moving a box upward through the use of a pulley 21 cm in radius. If the pulley is rotated counterclockwise through an angle of 120

To Find:

what is the height, that the weight will rise

Solution:

It is given that the pulley is of radius 21 cm and it is being rotated counterclockwise, if so then the object at the end of the rope of the pully will rise up by the same length the pully will cover in rotating 120 degrees.

If a circle rotates some degrees then the length covered by the circumference will be equal to the length of the arc it makes. So in this case an arc with central angle 120 is made, to find the length of an arc we use a formula that is,

                                 $length=2\pi r\frac{\theta}{360}$

where,

          r= radius of the arc

          theta= central angle of the arc

now put the values, we have

$length=2*\frac{22}{7} *21*\frac{120}{360}\\=44cm$

Hence, the height the weight will rise is 44cm.