Motion in Physics – Definition, Laws, Types of Motion

What is motion?

Motion is the fundamental concept in physics that describes how things move and their changes in location with respect to a frame of reference. Motion helps in scientific fields, including physics, engineering, astronomy, and even everyday experiences. It helps describe and predict how objects behave and interact in the world around us.

“An object is said to be in a state of motion if its position changes with time with respect to its surroundings.”

What are the different types of motion?

We observe different types of motion around us.

  • Translatory Motion
  • Rotatory Motion
  • Oscillatory Motion
  • Multiple or Complex Motion
  • Random Motion
  • Periodic Motion
  • Nonperiodic Motion
  • uniform Motion
  • Nonuniform Motion

Translatory Motion

If an object moves on the whole from one place to another, so that each part of it moves the same distance in a given time, then the object is said to be in translatory motion.

Translatory motion is of two types.

  1. Rectilinear motion
  2. Curvilinear motion

Rectilinear motion – If the motion of an object is along a straight path, it is said to be in rectilinear motion.

Curvilinear motion – If the motion of an object is along a curved path, it is said to be in curvilinear motion.

Ex – A football kicked by a player moves in a curvilinear motion.

Circular motion is the special case of curvilinear motion. In circular motion, an object moves along a circular path.

Ex- The motion of the moon around the earth and the whirling of a stone tied to a string is example of circular motion.

Rotatory Motion

If an object moves about a fixed axis or a fixed point, without changing its position on the whole, then the object is said to be in rotatory motion.

Examples

  • Spinning Top: A spinning top rotates around its central axis.
  • Earth’s Rotation: The Earth rotates around its own axis, causing day and night cycles.
  • Rotating Fan: The blades of a fan rotate around a central hub when it’s turned on.
  • Car Wheels: When a car moves, the wheels rotate around their axles to propel the vehicle forward.

Oscillatory Motion

If an object moves to and from about its mean position, then the object is said to be in oscillatory motion.

  1. Pendulum: A simple pendulum swings back and forth under the influence of gravity.
  2. Heartbeat: The rhythmic contraction and relaxation of the heart muscle represent oscillatory motion.
  3. Tides: The water level to rise and fall rhythmically.
  4. Motion of a Playground swing.
  5. Movements of the needle of a sewing machine.
  6. Motion of the piston of an engine.

Vibratory Motion is the special case of Oscillatory motion, the motion of an object in which only a part of the object moves to and from about its mean position while the remaining object remains at rest, is called vibratory motion.

Multiple or Complex Motion

When an object simultaneously shows a combination of two or more types of motion, then this combination of motion is called multiple or complex motion.

  1. A car moving on a road as whole shows translatory motion, but its wheel show rotatory motion.
  2. A ball sliding down a smooth inclined plane shows both translatory and rotatory motion.
  3. A drill used by a carpenter for drilling a hole in wood has both translatory and rotatory motions.

Random Motion

When an object has no specific path and frequently changes its motion, the motion is called random or irregular motion.

In random motion, the moving object may have translatory motion at one moment and rotational motion at the very next moment, and the direction of motion is also changed frequently.

Examples

  1. Motion of flying mosquito or fly.
  2. Motion of a hockey or football player.
  3. Motion of a flying kite.
  4. Motion of smoke particles.

Periodic Motion

Sometimes a motion repeats itself again and again after a fixed interval of time. this type of motion is called periodic motion.

Examples

  1. Motion of the hands of a clock.
  2. Vibrations of strings of musical instruments.
  3. Rotation of the earth around its own axis are all periodic in nature.
  4. Heartbeat and pulse are also examples of periodic motion.
  5. Alternating current.

Nonperiodic motion

A motion which does not repeat itself at regular intervals of the time is said to be nonperiodic motion.

Examples

  1. A man walking in a park.
  2. motion of an athlete.
  3. motion of a vehicle on road.
  4. Turbulence in Fluids.

Note: in some cases, motion may be repetitive but may not be periodic.

Uniform Motion

The motion of a moving object is said to be uniform, if it covers equal distance in equal intervals of the time along a given straight path.

Ex – A car is in a motion which covered a distance of 40 km in each one hour as shows in below image.

Nonuniform Motion

The motion of a moving object is said to be nonuniform, if it covers unequal distance in equal intervals of the time while moving along a straight path.

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