Topics
Location and Transformation
topic badge
India
Class VII

Rotations I

Lesson
Practice
Lesson

A rotation is what occurs when we turn an object or shape around a central point.  The object is exactly the same shape and size, just spun around (like going in a circle). Every point on the original shape has a matching point on the new shape. 

Commonly we describe rotations using a degree measure (like an angle), and as being either clockwise or anticlockwise.

Particularly at the moment you need to be able to identify rotations of:

$90^\circ$90° (a quarter turn), $180^\circ$180° (a half turn), $270^\circ$270° (a three-quarter turn) and $360^\circ$360° (a full turn) in both clockwise and anticlockwise directions.  

Have a play with this interactive. Here you can change the shape that of the object and the position of the central rotation point. Notice how a rotation of $360^\circ$360° takes you right back to where you started.

Created with Geogebra

Examples

Question 1

Which picture shows a rotation?

Think: Which one looks like it has been spun around?

Do:

C has been translated (slid) into a different position. 

B looks like a mirror image of the original. So this is a reflection (flip).

A has been spun around $180^\circ$180°. This is the rotation!

Question 2

Select all the rotations.

  1. A

    B

    C

    D

QUESTION 3

Which of the following figures represents the given flag after rotating it anticlockwise around the red point by 90° ?

A square grey flag with a flag pole on a grid plane is depicted. It is represented by a square with a vertical line segment extending from its right side 1 unit downward, representing the flagpole. The end of the flagpole has a red point indicating its center of rotation.
  1. A square grey flag with a flag pole on a grid plane is depicted. It is represented by a square with a horizontal line segment extending from its top side 1 unit to the right, representing the flagpole. The end of the flagpole has a red point indicating its center of rotation.
    A
    A square grey flag with a flag pole on a grid plane is depicted. It is represented by a square with a vertical line segment extending from its left side 1 unit upward, representing the flagpole. The end of the flagpole has a red point indicating its center of rotation.
    B
    A square grey flag with a flag pole on a grid plane is depicted. It is represented by a square with a horizontal line segment extending from its bottom side 1 unit to the left, representing the flagpole. The end of the flagpole has a red point indicating its center of rotation.
    C
    A rectangle grey flag with a flag pole on a grid plane is depicted. It is represented by two squares stacked vertically with a vertical line segment extending from its right side 1 unit downward, representing the flagpole. The end of the flagpole has a red point indicating its center of rotation.
    D

QUESTION 4

Which is the correct image after the original is rotated by $45^\circ$45° clockwise?

Five triangles are shown on a grid labeled "ORIGINAL", "A", "M", "H", and "B", and shaded in red, green, blue, purple and yellow respectively. A point labeled "central point" is shown indicating a pivot point. "A", "M", "H", and "B" are rotation of "ORIGINAL". The ORIGINAL triangle has a horizontal longest side at the bottom and has an opposite vertex at the top. Triangle A has a slanted longest side and the opposite vertex and another vertex are horizontally aligned to the central point. Triangle M has a vertical longest side and has an opposite vertex at the right. Triangle H has a horizontal longest side at the top and has an opposite vertex at the bottom. Triangle B has a vertical longest side and has an opposite vertex at the left. The original triangle is positioned on the upper right of the central point.

  1. $B$B

    A

    $M$M

    B

    $H$H

    C

    $A$A

    D

Outcomes

7.G.S.2

Idea of rotational symmetry, observations of rotational symmetry of 2-D objects. (90, 120, 180 degree)

7.G.S.3

Operation of rotation through 90 and 180 degree of simple figures.

What is Mathspace

About Mathspace