Question

Find the mechanical advantage of the system of the figure showing block and tackle system pulleys to lift a road.


(A) 6
(B) 8
(C) 4
(D) 2

Answer 1

Hint: The mechanical advantage can be defined as the calculation which measures the amplified force taken by the mechanical system. It is the ratio of the force of an object to the effort to overcome the force of an object.
Formula used: - As the mechanical advantage is the ratio of load of object to effort to overcome the load so, mechanical advantage is calculated by –
$M.A = \dfrac{{load}}{{effort}}$

Complete step by step solution:
The type of calculation which measures the amplified force gained by the mechanical system is called mechanical advantage. It can be calculated by dividing the force applied to the load and force required to overcome the given force. The mechanical advantage is the unitless parameter. The efficiency of a machine is equal to the ratio of its output to its input. It is also equal to the ratio of the actual and theoretical mechanical advantage.
As this question is about pulley, so we should know something about it. Therefore, pulley is the wooden or metallic machine which uses ropes and wheels. This machine is used to lift heavy loads. There are two types of pulley:
1. Fixed pulley – The type of pulley whose block is fixed in the high platform is known as fixed pulley. The string passes from the groove where its one end is attached to the body to be lifted and its another end is free.
2. Moveable pulley – The moveable pulley can be defined as the pulley which can be moved or whose block is not fixed. In this pulley the inextensible string is used for carrying the loads and process is same as the fixed pulley.
As we know that, mechanical advantage for pulley is the ratio of load to the effort –
$M.A = \dfrac{{load}}{{effort}}$



So, from the figure we can see that –
$load = 4T$ and $effort = 1T$
Putting the values of effort and load in the formula of mechanical advantage, we get –
$
  M.A = \dfrac{{4T}}{T} \\
  \therefore M.A = 4 \\
 $

Hence, the mechanical advantage is equal to $4$. Therefore, the correct option is (C).

Note: A block and tackle is an assembly of a rope and pulleys that is used to lift loads. A number of pulleys are assembled together to form the blocks, one that is fixed and one that moves with the load. The rope is threaded through the pulleys to provide mechanical advantage that amplifies that force applied to the rope.