# Help Zone

### Student Question

Secondary II âą 2yr.

Hello,

I am having a hard time with the motion transformation mechanisms. Could you explain them to me please?

Thanks a lot!

Science

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## Explanations (1)

• Explanation from Alloprof

Explanation from Alloprof

This Explanation was submitted by a member of the Alloprof team.

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Team Alloprof âą 2yr.

Thank you for your question!đ

A motion transformation mechanism transmits and modifies motion from one part of an object to another. For example, the part the movement transmitted to a part changes from a rotation to a translation. Care must be taken to differentiate it from motion transfer mechanisms, which transmit movement without transforming it.

Here are a few motion transformation systems:

• Screw and nut

In this system, the rotation of one part is transformed into the translational movement of the other. This mechanism is said to be irreversible, because only the motor organ can initiate the movement. For example, if the screw is pulled, the nut will not turn. Here is a picture of the system:

• Connecting rod and crank

This mechanism transforms a rotational movement into a translational movement, which goes back and forth. The crank produces the rotational movement and the connecting rod makes the translational movement. The movement is reversible; the driving organ can be either the connecting rod or the crank. This system is usually found in gasoline engines.

• Rack and pinion

This mechanism transforms the rotational movement of the pinion into the translational movement of the rack. This system is reversible since the pinion and the rack can be the driving member. Here is a picture of the system:

• Cam and roller (or cam and push rod)

This mechanism transforms the rotational movement of the cam into the back and forth translational movement of the push rod. This movement is irreversible, because if the push rod pushes on the cam, it will not cause a rotation. Here is a picture of this system:

If you have other questions, do not hesitate to ask them on the forums.

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