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Motion and Measurement of Distances - Types of Motion: Rectilinear, Circular, and Periodic

Grade 6CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Motion is defined as the change in the position of an object with time with respect to a fixed point or stationary object.

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Rectilinear Motion: This occurs when an object moves along a straight line path. For example, a vehicle moving on a straight road or 100 m100\text{ m} sprinters in a race.

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Circular Motion: An object is said to be in circular motion when it moves along a circular path such that its distance from a fixed point (the center) remains constant. Examples include the motion of a point marked on the blade of an electric fan or the hands of a clock.

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Periodic Motion: This is a type of motion that repeats itself after a fixed interval of time. Examples include the motion of a pendulum, a child on a swing, or the strings of a guitar when plucked.

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Rotational Motion: This occurs when an object turns (rotates) about a fixed axis. For example, a spinning top or the rotation of the Earth on its axis.

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An object can possess more than one type of motion at the same time. For instance, a ball rolling on the ground undergoes both rectilinear motion (moving forward) and rotational motion (turning on its axis).

📐Formulae

Speed=Total DistanceTotal TimeSpeed = \frac{Total\ Distance}{Total\ Time}

v=stv = \frac{s}{t}

1 km=1000 m1\text{ km} = 1000\text{ m}

1 m=100 cm1\text{ m} = 100\text{ cm}

💡Examples

Problem 1:

Identify the type of motion in the following cases: (a) A branch of a tree swaying to and fro, (b) A stone falling vertically downwards, (c) The motion of the Earth around the Sun.

Solution:

(a) Periodic Motion, (b) Rectilinear Motion, (c) Circular and Periodic Motion.

Explanation:

The tree branch repeats its path at intervals (Periodic). The falling stone moves in a straight line (Rectilinear). The Earth moves in a near-circular path and repeats it every 36514365\frac{1}{4} days (Circular and Periodic).

Problem 2:

A car travels a distance of 200 km200\text{ km} in 4 hours4\text{ hours}. Calculate its speed using the formula Speed=DistanceTimeSpeed = \frac{Distance}{Time}.

Solution:

50 km/h50\text{ km/h}

Explanation:

Given Distance=200 kmDistance = 200\text{ km} and Time=4 hTime = 4\text{ h}. Plugging into the formula: 2004=50 km/h\frac{200}{4} = 50\text{ km/h}. This motion is usually rectilinear if the car is on a straight highway.

Problem 3:

Give an example of an object that undergoes both Rectilinear and Rotational motion simultaneously.

Solution:

A sewing machine needle and the wheel of the sewing machine.

Explanation:

The wheel undergoes rotational motion while the needle undergoes periodic motion (up and down). However, a better example is a rolling ball: it moves forward in a straight line (Rectilinear) while spinning (Rotational).