Question

The figure given shows a block and tackle system of four pulleys. Draw a string around the pulleys. Also, show the position and the direction of effort to be applied on this string. What is the mechanical advantage and velocity ratio of this system?

Answer 1

1. Velocity Ratio (VR):

The velocity ratio of a block and tackle system is equal to the total number of pulleys in the system (or the number of strands supporting the movable block).

Velocity Ratio (VR) = 4

2. Mechanical Advantage (MA):

In an ideal system (neglecting friction and the weight of the movable pulleys):

The load (L) is supported by 4 strands of string:

L = 4T

The effort (E) balances the tension in the free end:

E = T

Mechanical Advantage (MA) = `"Load (L)"/"Effort (E)"`

= `(4T)/T`

= 4