Question

A block and tackle system of pulleys has a velocity ratio of 4.
(i) Draw a labelled diagram of the system indicating clearly the points of application and direction of load and effort.
(ii) What is the value of the mechanical advantage of the given pulley system if it is an ideal pulley system?

Answer 1

Hint: We know how a block and tackle system of the pulley with a velocity ratio of 4 looks like. We need to draw the diagram of the required system as per the question. Now for the second part of the question, we know the value of the velocity ratio is 4 and we can see the value of load and effort in terms of tension. From the formula for mechanical advantage, we need to calculate the value.

Formula used:
M.A = Load / Effort

Complete step by step answer:
i)

Here in the above diagram, we see a set of pulley including the movable and immovable pulley, here the round figure marked as ‘L’ is the load and the end of the string where effort is given is marked as ‘E’. And all the ‘T’ represents tension on the string due to the effort given.

ii) We know that the velocity ratio is given as 4.
Now we can see that, Load = 4 T and Effort = T
We know that the formula for mechanical advantage is ,
M.A = Load / Effort.
$M.A=4T/T$
$M.A=4$.
Hence we can say that the mechanical advantage of the pulley system is 4.

Additional Information:
A pulley is basically a wheel with a rim that is grooved and around which a cord passes, which generally is acting to change the direction of the force applied to the cord and it is used to raise very heavyweights.

Note: Students must remember the diagram for the pulley system of block and tackle pulley for velocity ratio 4. They must always remember the formula for mechanical advantage, and they must know that mechanical advantage has no unit.