Question Set B – 1 to 10

Q.1. What is a fixed pulley? State its one use.
Ans. Fixed pulley: A pulley which has its axis of rotation fixed in position, is called a fixed pulley.
Single fixed pulley is used in lifting a small load like water bucket from the well.

Q.2. What is the ideal mechanical advantage of a single fixed pulley Can it be used as a force multiplier?
Ans.
The ideal mechanical advantage of a single fixed pulley is 1.
It cannot be used as force multiplier.

Q.3. Name the pulley which has no gain in mechanical advantage. Explain, why is such a pulley then used?
Ans.
There is no gain in mechanical advantage in the case of a single fixed pulley. A single fixed pulley is used only to change the direction of the force applied that is with its use, the effort can be applied in a more convenient direction. To raise a load directly upwards is difficult.

Q.4. What is the velocity ratio of a single fixed pulley?
Ans.
The velocity ratio of a single fixed pulley is 1.

Q.5. In a single fixed pulley, If the effort moves by a distance x downwards, by what height is the load raised upwards ?
Ans.
The load rises upwards with the same distance x.

Q.6. What is a single movable pulley? What is its mechanical advantage in the ideal case?
Ans.
Single movable pulley: A pulley, whose axis of rotation is not fixed in position, is called a single movable pulley.
Mechanical advantage in the ideal case is 2.

Q.7. Name the type of a single pulley that has an ideal mechanical advantage equal to 2. Draw a labelled diagram of the pulley mentioned by you.
Ans.

Q.8. Give two reasons why the efficiency of a single movable pulley is not 100%.
Ans.
The efficiency of a single movable pulley system is not 100% this is because
(i)The friction of the pulley bearing is not zero ,
(ii)The weight of the pulley and string is not zero.

Q.9. In which direction does the force need to be applied, when a single pulley is used with a mechanical advantage greater then 1? How can you change the direction of force applied with out altering its mechanical advantage? Draw a labelled diagram of the system.
Ans.
The force should be in upward direction.
The direction of force applied can be changed without altering its mechanical advantage by using a single movable pulley along with a single fixed pulley to change the direction of applied force.
Diagram:

Q.10. What is the velocity ratio of a single movable pulley? How does the friction in the pulley bearing affect it?
Ans.
The velocity ratio of a single movable pulley is always 2.

Q.11. In a single movable pulley, if the effort moves by a distance x upwards, by what height is the load raised?
Ans.
The load is raised to a height of x/2.

Q.12. Draw a labelled diagram of an arrangement of two pulleys, one fixed and other movable. In the diagram, mark the direction of all forces acting on it. What is the ideal mechanical advantage of the system? How can it be achieved?
Diagram:

Ideal mechanical advantage of this system is 2. This can be achieved by assuming that string and the pulley are massless and there is no friction in the pulley bearings or at the axle or between the string and surface of the rim of the pulley.

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