Advertisements
Advertisements
Question
Give reason for the following:
In a single fixed pulley, the velocity ratio is always more than the mechanical advantage.
Advertisements
Solution
In a single fixed pulley, some effort is wasted in overcoming friction between the strings and the grooves of the pulley; so the effort needed is greater than the load and hence the mechanical advantage is less than the velocity ratio.
RELATED QUESTIONS
Name a machine to change the direction of force ?
Explain how a gear system can be used to obtain gain in speed? Given one example.
Define the following term in reference to a gear system for Gear ratio ?
Define the following term in reference to a gear system for Gain in torque ?
Name the type of single pulley that can act as a force multiplier. Draw a labelled diagram of the pulley mentioned by you.
The diagram below shows a pulley arrangement.
- Name the pulleys A and B.
- In the diagram, mark the direction of tension on each strand of string.
- What is the purpose of the pulley B?
- If the tension is T, deduce the relation between
- T and E, and
- E and L.
- What is the velocity ratio of the arrangement?
- Assuming that the efficiency of the system is 100%, what is the mechanical advantage?

The diagram below shows an arrangement of three pulleys A, B, and C. The load is marked as L and the effort as E.
- Name the Pulleys A, B, and C.
- Mark in the diagram the directions of load (L), effort (E) and tension T1 and T2 in the two strings.
- How are the magnitudes of L and E related to the tension T1?
- Calculate the mechanical advantage and velocity ratio of the arrangement.
- What assumptions have you made in parts (c) and (d)?

What is a block and tackle system of pulleys?
If the weight of the movable pulley is W, obtain the expression for MA, VR, and efficiency.
