Lesson Notes By Weeks and Term v4 - JHS 2

Lesson Video

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Performance objectives

• Define rotation and identify its properties.
• Describe the center and angle of rotation.
• Perform rotations of shapes on a coordinate plane.
• Identify real-life examples of rotation.

Lesson summary

Rotation is a fundamental concept in Geometry that describes the motion of 'turning' or 'spinning'. We see rotation all around us in Ghana, from the blades of a ceiling fan in our classroom to the wheels of a tro-tro on the road, and even in the beautiful patterns of our Adinkra symbols. Understanding rotation helps us describe movement accurately and is a building block for more advanced topics in mathematics, science, and design. In this lesson, we will explore what rotation is, how to describe it, and where we can find it in our daily lives.

Lesson notes

What is Rotation? Rotation is a type of transformation that turns an object or shape around a fixed point. Think about opening a door. The door itself moves, but the hinges stay in the same place. The door rotates around the hinges.

The original shape is called the object, and the shape after it has been turned is called the image. An important property of rotation is that the image is always congruent to the object. This means it has the same size and same shape; it has only changed its orientation (the way it is facing). The Three Essential Elements of Rotation To describe a rotation completely, you must state three things: The Centre of Rotation: This is the fixed point around which the object turns. It is the only point that does not move during the rotation. In our door example, the hinge is the centre of rotation. On a graph, this is often the origin (0, 0). The Angle of Rotation: This tells us how far the object has turned. It is measured in degrees (°). Common angles are: 90°: A quarter turn. 180°: A half turn. 270°: A three-quarter turn. 360°: A full turn (the object returns to its original position). The Direction of Rotation: This tells us which way the object is turning. Clockwise: The same direction that the hands of a clock move. Anticlockwise (or Counter-clockwise): The opposite direction to the hands of a clock.

*Unless stated otherwise, the direction for rotation is usually anticlockwise.*