Question

The Velocity Ratio (VR) of a block and tackle system of two pulleys with the effort in the upward direction is ______.

Options

• 1

• 2

• 3

• 4

Answer 1

The Velocity Ratio (VR) of a block and tackle system of two pulleys with the effort in the upward direction is 2.

Explanation:

The problem says that the block and tackle system has two pulleys (n = 2), which means that there are two of them. In a normal setup with two pulleys, one would be fixed in the upper block, and the other would be mobile in the lower block. Two parts of the rope are holding up the load. For every d_E that is pulled on the effort end of the rope, each of the two supporting rope pieces gets shorter by d_L. Therefore, the load moves up by a distance d_L, and d_E = 2 × d_L.

Using the formula for VR:

VR = `d_E/d_L`

= `(2 xx d_L)/d_L`

= 2

Alternatively, using the direct relationship for a block and tackle system:

VR = total number of pulleys = 2