Motion-And Its Movements


Motion-And Its Movements

Motion basically means movement of an object from one place or position to another over a period of time. There are various types of motion. They are:

  • Linear (in a straight path)
  • Rotary (in a rotatory form
Motion blur
motion blur
Train in Motion
Train in motion


Linear Motion

Linear motion could be horizontal or vertical. In engineering, it is possible to arrange mechanisms such that motion in a straight line is achieved. This can be done through the use of slots,slides,levers and linkage.

how to make slots bring about linear motion

  • Obtain an old biro
  • Remove the ink tube from the bore of the handle
  • Colour the ink tube with a suitable colour to make it visible.
  • Re-insert the ink tube into the bore of the biro handle with your right hand while holding the bore with your left hand in a fixed position.
  • Move the ink tube in and out of the bore.
  • Observe that the ink tube moves in a straight line guided by the bore boundaries,irrespective of change in the position of the moving hand.

how to obtain linear movement in a slot

  • Obtain a wooden cabinet or a filling cabinet.
  • Hold the handle of one of the drawers with one or both hands.
  • Move the drawer backwards(out) and forward(in).
  • Make that it does not move out more than half of its full length.



Rotary motion, unlike linear motion, is a kind of motion that takes place in a rotating form(Three hundred and sixty degrees). However, in some cases, rotary motion is not completely 360 degrees, but 90 degrees or more, but less than 360 degrees. A typical example of 90 degrees or more rotary motion is the handle or lock of a door. There are mainly two types of rotary motion:

  • One-way rotary motion
  • Reversible rotary motion

One-way rotary motion

Mechanisms or components that rotate in one direction, either clockwise or anti-clockwise are regarded as one-way rotary motion components.

Examples are:

  • Rotation of electric fans
  • Grinding machines and milling machines.

Here no harm is caused if the motion takes place in a reverse direction. However, there are instances in which any reversal may cause malfunctioning of the machine. The circular wood saw is a typical example. It should rotate in one direction so that cutting can be effective with reduced wear and tear on the blades. In bicycles, ratchets are used to prevent rotation of wheels in the reverse direction, while in clocks and wristwatches, gear teeth are used to prevent rotation in the reverse direction. These mechanisms perform one-way non-return rotary motions.

Reversible rotary motion

Mechanisms or components that can rotate in a clockwise direction or in an anti-clockwise direction, carry out reversible rotary motion. Reversible motion has its advantage.

Examples are:

  • Cassettes and tapes, the rotation in one direction is used for playing the cassette, while rotation in the reverse direction is used for rewinding.
  • The wheels of most cars, forklifts, lorries and trains are able to perform reversible rotary motion because of the change from forward to reverse gears.



In producing machines and appliances, it is commonly necessary to convert rotary motion to linear motion. This is done by some mechanisms like linkages,threads and cams.


  • A door with a mortise lock in it.
    Mortise lock
    mortise lock

    how to convert rotary motion to linear motion 

  • Obtain a door with a mortise lock in it.
  • Locate the handle of the lock.
  • Turn the handle and observe how the locking device moves linearly. As the lock handle moves downward, the locking device is constrained to move in.

how to convert rotary motion in a vice



  • Obtain a bench vice
  • If the jaws are closed, turn the handle anticlockwise, but if the jaws are open, turn the handle clockwise.
  • Observe that as the handle turns, jaw A moves in a linear motion constrained or guided by the slides of jaw B.
  • Turn the vice upside down and turn the handle. Observe and describe how the rotary motion of the handle is converted to linear motion by jaw A.



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