Reversible and Irreversible Systems - Secondary 3

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Reversible Systems

Definition

A reversible system is a system where the driver component can become the driven component and vice versa.

A system is said to be reversible when its different components can perform different functions. A driver component (or driving unit) can become a driven component (or receiving unit) and vice versa.

Be careful!

The reversibility of a system is not related to the direction of rotation of its components.

A system where the direction of rotation can be changed is not necessarily reversible.

The following are the reversible systems studied at the Secondary level.

Examples

This gear train is reversible because both wheel gears can act as the driver or driven component.

Therefore, the rotational motion of the blue wheel gear can drive the rotational motion of the yellow wheel gear.

Alternatively, the rotational motion of the yellow wheel gear can drive the rotational motion of the blue wheel gear.

A gear train is a reversible system. Both gears can act as the driver or the driven component.

A gear train system

A bicycle transmission uses a chain and sprocket system. The pedal gear is called the crankset and the rear wheel gear is called the rear sprocket. The system is reversible because both the crankset and the rear sprocket can act as the driver or driven component.

Therefore, the rotational motion of the crankset can drive the rotational motion of the rear sprocket using the chain as an intermediate component.

Alternatively, the rotational motion of the rear sprocket can drive the rotational motion of the crankset using the chain as an intermediate component.

The bicycle transmission is reversible. Both the crankset connected to the pedals and the rear wheel sprocket can act as the driver or driven component.

A chain and sprocket system in a bicycle

Tip

To determine if a system is reversible, the following questions should be answered.

  • Can the driver component become the driven component?

  • Can the driven component become the driver component?

If the answers are yes, the system is reversible.

If the answers are no, the system is irreversible.

Irreversible Systems

Definition

An irreversible system, also called a nonreversible system, is a system that can only be activated by one component, called the driver component (or driving unit).

In an irreversible system, the driver role can be assumed by only one component.

Important!

If a force is applied to the usually driven component, the component that is usually driving will not move. In most cases, the system will lock in place.

The following are the irreversible systems studied at the Secondary level.

A Worm and Worm Gear System: an Exception!

Example

A glue stick uses a screw gear system (type I). It is an irreversible system because only the screw can be the driver component, while the nut, attached to the glue support base, is always the driven component.

Therefore, the rotational motion of the screw drives the translational motion of the nut.

However, pushing on the glue and the support base does not drive the rotational motion of the screw. No motion occurs because the system is locked.

An irreversible screw gear system in a glue stick.

A screw gear system in a glue stick

Tip

To determine if a system is irreversible, the following questions should be answered.

  • Can the driver component become the driven component?

  • Can the driven component become the driver component?

If the answers are yes, the system is reversible.

If the answers are no, the system is irreversible.